Abstract: It is important to study the dynamics of microbial community and the characteristics of microorganisms during the composting. During this process, all kinds of microorganism quantity follow the high－low－high rule, and the quantity of microorganisms depends on the difference of thermotolerance. Generally speaking, the quantity of bacteria is most, especially during the thermophilic phase. The quantity of actinomycete and fungi increas faster before and after thermophilic phase. Opinion on the decomposing function of different microorganisms to different elements of substrate is no consistent. As for the effect of inoculation, favorable and opponent opinions are supported by a lot of evidences. It is fact that the process of composting can be improved only when enough useful microorganisms and optimal conditions for them to growth coexist, so it is necessary to establish useful microorganisms and to create the optimal conditions for microorganism growth.