Abstract: The definition of soil moisture dynamics is very important to improve the management of ryegrass pasture. The use of the environmental policy integrated climate (EPIC) model can improve the accuracy of cropping system simulations, thereby providing better information for decision making. In this study, field experiments and computer simulations were used to analyze the growth process of ryegrass and the dynamics of soil moisture in ryegrass pastures. Then, the accuracy of the EPIC model to simulate ryegrass growth and soil moisture was evaluated. The results showed that available soil water in the deep soil layer (0.4-0.6 m) was relatively lower from March to May, but increased from May to October. Appropriate nitrogen fertilization (75-225 kg/ha) significantly increased the forage yield and leaf area index of ryegrass pastures in the hilly region of Sichuan Province. The correlation index values between observed and simulated available soil water in the 0-1 m soil layer ranged from 0.86 to 0.95 with RRMSE values ranging from 6.0% to 17.2%. The range of correlation index values between observed and simulated soil water in the 0-1 m soil layer was 0.57-0.92, and most values were >0.85. The correlation index values between simulated and observed values of forage yield, leaf area index, and height of ryegrass were >0.90, and there were no significant differences between simulated and observed values. In conclusion, the EPIC model can simulate soil moisture and forage yields of ryegrass pastures. These simulations can be used to evaluate the suitability of grain-forage cropping systems for the hilly regions of Sichuan Province.