Dielectrowetting is a powerful technique in manipulation of droplet. The key feature of dielectrowetting is the ability of a non-uniform and decay electric field to reversibly alter the energy balance of a droplet above a solid surface and change the contact angle of the droplet by employing microfabricated interdigitated electrodes. The contact angle versus voltage is presented and the effects of using different AC frequencies are also discussed. Special attention is dedicated to dielectrowetting-based light control system. The transmission spectrum of the light valve can be controlled with various voltages. This work facilitates us to improve and optimize the performance of light valve device operations.