Modeling of organic matter degradation and thermal balance were built based on the first order assumption with respect to the quantity of biodegradable volatile solid (BVS) and the law of thermal conservation during composting. Different kinds of organic matter were mainly degraded in different composting stages. For the organic matter degradation model, temperature, moisture content, oxygen content and free air space were considered as key influence factors to degeneration rate. For the model of thermal balance, forced convention and conduction were considered as the main heat removal form. In order to verify the constructed models, an aerobic composting process of pig slurry was conducted. Temperature, oxygen content, moisture content and organic matter concentration were all monitored in the process of composting. The results could be helpful for guiding composting process operation. 