Abstract: Modified point mass (MPM) model was introduced to predict the trajectory of spin-stabilized projectile. Error was analyzed when MPM model calculates a trajectory with large initial elevation. Theoretical analysis indicated that the modeled results error was mainly caused by deviation between gravity-induce trim angle and angle of attack(AOA). And gravity-induce trim angle showed an approximate linear correlation with the AOA. On that bases, extended Kalman filter was designed to compensate the model error and improve the trajectory prediction accuracy. The results of semi-physical simulation show that the accuracy of MPM model is obviously improved by error compensation. The impact point prediction error past the apogee is less than 20 m which means that the proposed method can meet the requirements of practical application.