Simulation models regarding moisture content were developed respectively by law of conversation of mass and first order assumption with respect to the quality of moisture content. Approaches by law of conversation of mass to moisture content prediction was based on an analysis of biologically produced water, exit gas content and inlet air content, with the biological water estimated from yield factors based on biodegradable volatile solid degradation. The other approach to moisture content prediction based on first order moisture evaporation kinetics was developed by an analysis of composting pile moisture content and aeration rate. An aerobic composting process of pig slurry and wheat straw was conducted in order to verify the models constructed. The experimental results showed that modeling results gave good accuracy, and the relative standard error of law of conservation of mass model and first order assumption model were respectively 8.01% and 8.86%.