The paper begins with the controlling time sequence of CCD camera and discusses two controlling methods of shutter time.The whole system were composed of CCD camera,main controlling unit,synchronization signal generating unit,signal disposing unit and monitor.Mega16SCM of AVR series was adopted as the main controlling unit while the threshold is setup by software to achieve close-loop control of shutter time,so as to give a new method to the design of light-adjusting systems.