Understanding the regulating mechanisms of the temperature sensitivity of soil organic carbon decomposition is essential to predict the future change of soil organic carbon pool under global climate change. Previous studies have reported that the quality of organic carbon and soil microbes play critical roles in organic carbon decomposition. However,the temperature sensitivity ( commonly referred to as Q_(10) ) of soil respiration remains uncertain,and is still hotly debated. In this study we performed an incubation experiment in the laboratory to estimate Q_(10) values of soil heterotrophic respiration,and to assess the roles of microorganism and substrate in the temperature sensitivity of soil organic matter decomposition. The results and conclusions of this study are summarized as follows: ( 1 ) We used sterilized soil as a carbon source and inoculated a small amount of fresh soil as microbial agent. Soil respiration after inoculated different microbes changed accordingly. We found the former respiration rate was lower than that of the latter, suggesting that soil carbon quality ( based on the content of dissolvable organic carbon) will affect soil respiration,the higher quality of soil carbon source,the stronger the soil respiration. ( 2) Compared with not sterilized samples,the Q_(10) value of sterilized soil after inoculation of the same fresh soil reduced significantly. This result proved that carbon source quality plays an important role on the temperature sensitivity,the higher carbon quality,the lower Q_(10) of carbon decomposition. The Q_(10) of sterilized soil inoculated with microbes of high Q_(10) increased accordingly,and the Q_(10) of sterilized soil inoculated with microbes of low Q_(10) decreased. This variation in Q_(10) revealed that microorganism is one of key factors affecting the temperature sensitivity. In acid soils,the contribution of microbes to Q_(10) was greater than that of carbon source,with 63. 2% from microbial source and 36. 8% from carbon source. In alkaline soils,the contributions were 41. 8% and 58. 2%,respectively.