Abstract: Circular synthetic aperture sonar(CSAS) is a high-resolution underwater imaging technique whose imaging performance is highly sensitive to the accuracy of platform position and attitude. However, in practical survey operations, unmanned platforms are often affected by environmental disturbances such as ocean currents and waves, causing deviations from the ideal trajectory and resulting in position and attitude errors, which significantly degrade imaging quality. Existing CSAS motion compensation methods mainly rely on underwater acoustic positioning systems to obtain the platform position. However, such methods usually require the deployment of additional acoustic transponders or base stations, resulting in complex system deployment and a strong dependence on external equipment. To address this issue, a CSAS platform motion compensation method based on multi-sensor fusion of the global positioning system(GPS) and the inertial navigation system(INS) is proposed in this paper. By integrating the position information obtained from GPS with the attitude data provided by the INS, the spatial pose of the sonar platform can be jointly estimated, and the spatial position of the sonar array can be corrected accordingly, thereby reducing the influence of platform motion errors on the imaging results. Simulation studies are conducted to analyze the effects of platform motion errors on imaging performance, and lake experiments are further carried out to validate the effectiveness of the proposed method. The experimental results demonstrate that the proposed approach can effectively compensate for motion errors caused by platform movement and significantly improve the imaging quality of CSAS. The proposed method does not rely on external underwater acoustic positioning systems and instead utilizes only the onboard navigation sensors of the platform to achieve effective motion compensation. This provides a simple and practical solution for high-resolution CSAS imaging in complex environments.