Abstract-In this paper, the angular side-play amount created by radiation pressure acting on active space object has been detailed investigated based on the physical optics, and the results are compared with the results by Mie theory; the correctness of the physical optics model is validated. The curves of angular side-play amount varied with the energy density of incident wave, mass of the object, and the angular between the direction of incident wave and initial velocity of the space etc. Using the results having been calculated, we analyzed the detectable conditions of angular side-play amount. A new method, which identifies different active object in space, has been taken out.