Abstract: In order to meet the requirements for high-precision pointing and stability of 2-D fast steering mirror(FSM) in fields such as laser communications, a systematic study was conducted on the angle calibration technology of 2-D FSM. A set of 2-D FSM angle calibration system was designed, and an innovative calibration algorithm was proposed. A least squares optimization idea was introduced into cubic spline interpolation, and the performance was significantly improvised by dynamically adjusting the optimization weight of the spline function. The interpolation accuracy was improved while taking into account the smoothness of the curve, and the limitations of traditional calibration methods was overcome. The theoretical analysis and experimental verification were then conducted. Experimental results show that within the angle range of ±1°, the optimized cubic spline interpolation method suppresses the Runge phenomenon, and the positioning accuracy root mean square error of the FSM in the azimuth and pitch directions is 1.54″ and 1.26″ respectively, which is better than the 5.02″ and 4.87″ of the polynomial fitting method. This study provides a reference for the high pointing accuracy and high stability control of the 2-D FSM.