Obtaining accurate carrier attitude information is the key to improve carrier navigation and positioning. In view of the nongravity acceleration interference caused by accelerated motion, which cannot be solved by the traditional filtering algorithm, a posture solution method based on Mahony and improved Kalman fusion is proposed. Firstly, the data obtained by inertial measurement unit is used for Mahony solution, and the result is used as the measurement information of improved Kalman. Secondly, through the gyroscope solution, the result is used as the state information of the improved Kalman to realize the attitude solution. The experimental results show that compared with the traditional method, the solution accuracy of the method proposed in this paper is improved by more than an order of magnitude, which can effectively suppress the high-frequency noise of drift error, greatly improve the solution accuracy of carrier attitude angle, and has good convergence.