Abstract: In order to investigate the changes of the concentrations of free gossypol (FG), crude protein (CP) and acid soluble protein (ASP) in the solid-state fermentation of cottonseed meal by Bacillus subtilis Bs-1, the temperatures, moisture contents, as well as the concentrations of CP, ASP and FG were measured in windrow-type aerobic fermentation. A growth model of Bs-1 was established using the equation of logistic. The kinetic models of cottonseed meal fermentation were built by accessing the correlation between the growth of B. subtilis Bs-1 and the contents of CP, ASP, and FG. Results showed that both temperature and moisture had regular changing trends in the process of fermentation. The concentrations of CP and ASP increased by 9.28% and 46.51%, respectively, whereas the FG content dropped by 42.31% after fermentation. Correlations between Bs-1 number and CP (R2=0.831)/ASP (R2=0.867) were positive. The Bs-1 population was negatively correlated with FG content (R2=0.976). The predicted values of the models agreed well with the experimental values in the verification experiment. The models can be used to predict the fermentation coursed by Bacillus subtilis Bs-1 under industrial-scale solid-state fermentation.