In view of the problems that increasing the sample number will reduce system attitude updating frequency and bring large coning error,while enhancing sampling frequency will increase the burden of navigation computer hardware,we proposed a modified conic error compensation algorithm.The angle increment information of the first two cycles' gyro output and the gyro sampling values of the current moment are used for coning error compensation by means of superimposed sampling,and the compensation factors are obtained according to the principle of minimum error.The algorithm not only improves system attitude updating frequency,but also reduces the coning error caused by equivalent rotation vector method.Therefore,the precision of attitude algorithm is improved.