In adverse circumstances such as mechanical vibration environment, it becomes a difficult technique problem to stabilize light-beam, which restricts the improvement of performance of optical systems. An analytical model of response of optical system's light-beam misalignment on platform ground vibration was established based on matrix optics, vibration theory and finite element method. And a numerical simulation analysis of an optical system was given in detail. The results showed that to increase the damping coefficient of the platform structure could effectively stabilize light-beam. Using flexible sustained platform can decrease the relative misalignment, but the misalignment caused by the exciting vibration on the platform woula increase. Therefore, in adverse circumstances, the light-beam stability control is the key technique to improve the performance of optical system.