Chalcidoids (Hymenoptera:Chalcidoidea) are important and significant natural enemy insects in biology control. They have been playing important roles in the natural control of many harmful insect pests in agriculture and forest, and using in biocontrol. Forest deforliators are some of the most destructive pests in Chinese forest and make serious economical losses every year. In order to carry out the policy –insect pests IPM should gives priority to biocontrol-made by Chinese State Forestry Administration in controlling forest plant dieseases and insect pests, and develop biocontrol, author have taken taxonomy research on hymenopterous parasitoids of forest deforliators (mainly lepidopterous insects) in China. This paper describes 109 chalcidoid species, belonging to 10 family, 40 genera, which parasitize Chinese forest deforliators. It includs one new genus, 49 new species, and five genera new to China, in addition, 15 new Chinese record species and 45 known species have been re-described. It comprises four parts: summary, material and method, result and discussion. In the first part, the taxonomic history is briefly reviewed; the worldwide study survey of chalcidoids parasitizing forest deforliators is carried out; and chalcidoids morphological character and their biology are summarized. In the second part, material collecting, preserving and mounting methods are introduced. The third part involves chalcidoids 109 species parasitizing different developing phase of forest deforliators. Each generic and specific characters are detailedly described, and their biology, hosts and distributions are given. Some main species are given their morphological pictures and SEM photos. The last part puts forward advice to the work of current field in the future. Meanwhile the paper are attached detailed references, and listed index chalcidoids –forest deforliator host and forest deforliator host -chalcidoids .