EPIC model has been evaluated and used world wide, however there is still some disagreements on the simulation results of nitrogen cycle. Based on field experimental data, simulation results of soil NO3-N was evaluated and the parameter sensitivity for simulated NO3-N was analyzed in irrigated winter wheat / summer maize field on the Loess Plateau of China. Results showed 1) EPIC model estimated soil NO3-N content and its movement among different soil layers well, with the mean RRMSE value of 0.46, for irrigated winter wheat / summer maize cropping system in the semi-humid region of the Loess Plateau. 2) Simulation results of soil NO3-N was more sensitive to soil parameters, compared with crop parameters and meteorological parameters. 3)To improve the parameter value of BN2, HI, TB, WA, CNDS, BD and FC was better to the EPIC model to simulate soil NO3-N on the Loess Plateau of China.