According to urban forest ecology, ecology economics, contamination ecology, landscape ecology, urban ecology and landscape architecture, Guangzhou urban forest ecosystem was investigated for its service and function effects, and its service value was evaluated as well. The data were colleted from urban forest ecology positioning station of Maofeng mountain, integrating line sampling, normal site investigating, data consulting and question survey, and the outcome of plants, water and soil sample by physiology and by chemical analysis. The results are as follows:Urban forest can be divided into several units of different class. The first class is category which decided by function type, the second is pattern by function aim, landscape feature, and the third is type by landscape and community feature. Then urban forest vegetation community was marked out according to plant composition and life type, and the urban forest classification system formed. That is urban forest-urban forest category (high unit)-urban forest pattern (middle unit)-urban forest type (base unit)-urban forest vegetation community (primary unit). In term of this, Guangzhou urban forest is divided into 6 categories, 17 patterns and 36 types, and Guangzhou urban forest classification system formed.Service effect valued projects were defined by urban forest service effect form, such as system ecologic function effect, system product effect, system society effect. Service categories were defined by the way of providing the urban forest ecological product, such as ecology product, production, etc., and function target, such as energy switching, nutrition element laying and restoring, climate adjusting, etc. Service effect indexes were integrated defined by urban forest ecologic service product, such as discharging O_2, fruit product, etc., and the function such as adding moisture and decrease temperature, nutrition accumulation. Index content was defined by the forming object of the service value. In light of this, urban forest ecology service value index system which is composed of 3 projects, 14 categories, 32 indexes and several index content was established.Results showed that, the solar energy absorbed and interchanged by Guangzhou urban forest ecosystem annually was 817438.61 × 10~8KJ, corresponds to thermal energy of 2789169.40t normal coal. That is to say, it creates a mine of 2789169t normal coal for Guangzhou people.Actually, Guangzhou urban forest ecosystem fixed carbon of CO_212741404t each year and discharge 9301224.92t O_2. Live organism and the fallen can fix CO_2 of 13363740t each year. Mineralized carbon and activated carbon of CO_2 were 7551856.89t in soil each year. Soil discharge 8174193t CO_2 each year.The nutrition elements accumulated in dry organism of Guangzhou urban forest ecosystem were as follows: N49196.6t, P4255.lt, K43943.6t. and 35521.69tN, 2162.88t P, and 15209.95t K would go back to soil each year.In 2003, 104846.38 × 10~4t water was hold by Guangzhou urban forest crown, 10246.98 × 10~4t by forest land, and 66183.44 × 10~4t by forest. The flux of exporting soil from forest land was 173913.50 × 10~4t. The wood evaporation was 313030.61 × 10~4t.Urban forest ecosystem can hold soil 1281096.3t/a every year; reduce abandon soilarea of 394.18hm2/a; reduce the lost nutrition in surface layer soil: N 1121.43t/a, P 662.41t/a, K 23284.49t/a, organic matter 25170.62t/a.In Guangzhou, the urban forest can absorb SO_2 28652.42t/a and make the atmosphere purified; the potential is 56826.09t/a. On average, HF 3240.45t/a and NO_2 1983.15t/a were absorbed. the capacity of stopping dust by the branches and leaves is 13275.98t every year.Urban forest can reduce the heat island effect obviously. Compared with the center of the city, the urban forest can reduce 2.1℃-3.4℃ in a fine day, and 0.7℃-2.5℃ in a rainy day, 2.37℃ on average. In Guangzhou, no matter what the weather is, the urban forest can enhance the humidity of atmosphere. When fine, the average humidity of the city zone was 9.3%-30.3% lower than that of the urban zone daily, and 7.8%-16.0% when rainy. The content of the atmosphere minus ion in forest is much more than that in city zone. The concentration variation of the minus ion in urban forest is 712 -20807each cubic centimeter, while only 15 -92 in the center of the city. The daily ultraviolet radiation index in month was reduced by 0.31-6.00 in fine days and 0.39-9.12 in rainy days. And the reduced radiation of heat was 0.01-12.53MJ/m2 daily in fine days and 1.1 -11.94MJ/m2 daily in rainy days. Compared with the city zone, the daily tiptop temperature in urban forest was reduced by 3.4℃, and comfortable days increases by 36.36%, relatively comfortable days increases by 28.57%; lightly uncomfortable days reduces by 8.38%; lightly frowziness days reduces by 21.42%; the frowziness days reduces by 66.80%. So the effect of urban forest to improve comfortable environment and optimize the quality of environment is notable.1% greenbelt increment in Guangzhou urban forest would create appended 12.16yuan/m2 of realty. Citizen will take 0.98% of expense to compensate the useful effect of free park, plaza, street landscape around city. Each year the increment of wood volume would be 343110.86m3, and bamboo 629.10 × 104roots/a, production of economic wood fruit 170020t/a. Employment chances created by urban forest issues were 55120.In 2003, the overall ecological service value of Guangzhou urban forest ecosystem was 4263700.01 × 10~4yuan, that is 12.19% of the local omni-production value, and 399.861% of the first industrial. The value arrange of each category is: a adjusting urban climate, 52.28% of the omni-value, b improving environment, 13.40%, c relaxation,7.388%, d ecological products, 4.712%, e purgation of water, 4.027%, f nutrition laying in, 2.471%, g production, 2.460%, h energy switch-laying, 2.355%, j culture education, 2.324%, j fixing carbon (CO_2), 2.247%, k employment, 1.942%, 1 water improving, 1.660%, m nutrition element rotation, 1.499%, n atmosphere purgation, 0.634%, o retaining soil, 0.471%, p biological diversity preserving and exploiting, 0.419%, q science popularization, 0.007%. The ratio of ecological, social and production value in the ecosystem is 93.26:4.28:2.46. The ecological one is 31.99 times as much as that of production, and 18.40 times of social value.The innovations in this paper are:a, systematic research on service function and values of urban forest ecosystem in an urban zone. And the ratio of its service value in omni-production was analyzed.b, methodologically, it provided a effectual way to calculate urban forest resource value for green GDP, basing on service value project of urban forest ecosystem, referencing data of 2003 was used to evaluate the service value,