In order to meet the testing need of rad level stabilization accuracy of high-precision EO stabilized sighting system in future,a method for testing the stabilization precision based on interferometer was proposed. According to the influence of the optical path difference of the two beams with the same source in the Twyman-Green interferometer on the interference fringe,the slight change of the interference fringe was observed utilizing the charge coupled device (CCD),as a result, the measurement of the stabilization precision was realized. By utilizing this measuring method, the aiming precision of the fast steering mirror (FSM) and the stabilized precision of a certain type of EO stabilized product were measured . Results show that the measurement precision can achieve 0.2 rad with our method.