The output frequency of signal in high-precision inertial navigation is limited， which is difficult to meet the accuracy requirement of control system for mobile satellite communications.To solve the problem， an attitude estimation algorithm with Sage-Husa adaptive Kalman filter based on data fitting interpolation is presented.It uses cubic spline interpolation to increase the output frequency of attitude information and increase the system estimation times per unit interval.The adaptive Kalman filter algorithm is used for constantly revising the filtering error and avoiding the possible filter divergence caused by system parameter mismatching.The experiment result shows that:1) Data fitting interpolation can make up for the deficiency of the high-precision inertial navigation in data update frequency， and the adaptive filtering can improve the robustness of the system to different environment;and 2) The attitude estimation and control accuracy of antenna beam attitude are improved significantly， which can satisfy the beam pointing needs of broadband mobile satellite communications.