| Liquid crystal elastomer (LCE) has a wide range of applications in energy conversion, soft robotics and non-contact control because of its properties such as fast photothermal response and reversible deformation. In this paper, the dynamic model of LCE simply-supported beam is established to study its bending vibration phenomenon under periodic light illumination by taking advantage of the property that liquid crystal elastomer can be coupled with mechanical deformation under external light stimulation. The light-driven control equation of the LCE simply supported beam is firstly established, and then the semi-analytic solution of the equation is obtained by the vibration superposition method, and then the change law is programmed by Matlab software. The calculation results show that the periodic light can cause the LCE simply supported beam to vibrate periodically, the vibration amplitude in the beam span can be adjusted by damping factor, thermal relaxation time, light intensity, light period and light rate, the vibration equilibrium position can be adjusted by light intensity and thermal relaxation time, and the vibration response time can be controlled by thermal relaxation time and damping. The results of this paper have some guiding significance for the control of light-driven motion and the design of light-mechanical energy conversion system.