The beam scanning method based on the Risley prisms can realize the arbitrary pointing of the beam in the field of view by the coaxial independent rotation of the prism group. It is widely used in laser radar, infrared countermeasures, optical reconnaissance and other fields for its compact structure, high pointing accuracy, low power consumption, and rapid response. Experimental results show that the spiral scanning method can meet the indicators of controllable field of view, controllable coverage, controllable period, and stable speed. However, there is still a certain sudden change in the speed of the prism near the maximum opening angle and the minimum opening angle, due to the scan trajectory setting and the limitation of the motor’s maximum speed, acceleration, etc. , resulting in excessive servo control errors. In order to solve the problem, an optimization method based on the combination of filtering and interpolation for the scan trajectory is proposed. Experiments show that the rotation speed of the prism after optimization tends to be smooth, and the maximum servo control error is reduced from about 1 200″ to about 300″, which is as small as 1/4 of the original. This method reduces the follow-up servo control error caused by the sudden change in the speed of the prism, optimizes the rotation process of the prism, reduces the jitter caused by the sudden change in the speed of the prism, and is beneficial to improve the scanning accuracy of the system.