The traditional offline inertia identification methods have low calculation accuracy and limited application occasions. Aiming at this problem, an improved off-line inertia identification method is proposed. Acceleration and deceleration programming with the torque calculation method is introduced into the identification process, and the effects of friction and load are eliminated, so that the accuracy of identification results is improved. A calculation model is established for the offline inertia identification of servo system. The proposed method is experimentally verified. The results show that this method can effectively improve the identification accuracy, and it also applies to the loaded case.