Pyrolysis technology of medical waste is drawing more and more attention because of being harmless, minimum and reusable. It is very important to investigate the characteristics of weight loss and heat change during the thermal decomposition of the medical waste. By using the TG-DTA apparatus, this paper attempts to complete a systematic research on the main influential factors effecting the thermal weight loss for single component medical wastes, the law on how mixing ratio effecting thermal weight loss for double component medical wastes, and the thermal changes in the process of thermal decomposition of the medical wastes. The main work and results are listed as follows.1. The main influential factors effecting the thermal weight loss of the single component medical wastes are investigated systematically.The experimental results indicate: Different samples show different parameters representing thermal weight loss; Generally speaking, the higher the heating rates, the higher the initial and finial temperature, the wider the reaction interval, the higher the peak height; The more the mass is, the higher the finial temperature is and the wider the reaction interval becomes, and the boundaries between the different thermal reaction become indistinct, and the weight loss ratio gets low; The thermal decomposition degree of the medical waste increases with the increase of the end-temperature. However, such effect becomes more indistinct when the temperature goes higher. The effect can be neglectable when the temperature exceeds 700℃; Generally speaking, the longer the heat-insulation time is, the higher the thermal decomposition degree of the medical wastes becomes. And the heat-insulation time has more obvious effect on those samples with easy pyrogenation than the others; According to experimental results, the suitable heat-insulation time is suggested to be under 30 minutes.2. The effect of the mixing ratio on the characteristics of double component samples has also been investigated, and the results indicate:⑴The effect of mixing ratio on the thermal decomposition degree varies with the different double component medical waste samples;⑵For most samples, initial-temperature and finial-temperature are determined by the component with more quantity;⑶Mixing ratio has remarkable influence on the reaction interval, as a result, when designing the medical pyrolysis equipment, the ratio of each component in the wastes shall be brought into consideration fully;⑷The mixing ratio has little influence on the peak temperature of the double component mixture.3. Through the Differential Thermal Analysis on single component, double components, three components and four components samples, it indicates that there exists only heat-absorb peak on DTA curve, not heat-release peak. This explains that the thermal decomposition of medical waste is a heat-absorb process. What is more, the shape of the curve is complex, and does not appear symmetric. The base line shows deviation.4. By analyzing of the DTA curve, it seems that the temperature the maximum weight loss rate appears is lower than the temperature the instantaneous thermal balance appears. For most samples, the difference between is less than 10 degree.5. The pyrolysis dynamics model based on single component sample by PPM method is established and the further calculations have been done. It seems that the model coincides with experimental results of some samples, while appears obvious aberration for some other samples.