Abstract: Increasing the number of sample can improve the accuracy of error compensation while the rotation vector applied in strapdown inertial navigation system coning error compensation, however, limited with the performance of navigation computer, it is impossible to increase the number of sample sharply to gain high compensation accuracy. A new algorithm to improve the error compensation accuracy without adding more navigation computer cost was presented. By using the precurrent and pre-precurrent attitude information of strapdown inertial navigation system to modify the rotation vector, the new algorithm can gain more four order accuracy than the traditional one after analyzed theoretically and proven by an example. And the new algorithm does not cost more navigation computer resource additionally.