When CIDC1816 direct coupling-enhanced digital camera was collecting still images, the effects of image intensifier cathode voltage decay time on the electron-optical systems were analyzed in theory, and it was proved that cathode voltage decay time also had impact on screen brightness decay time. A method was proposed using the high-speed response characteristics of electronic switches to reduce cathode voltage decay time and improve this kind of digital camera time response characteristics. Using this method during the period of collecting still images, the results show that image intensifier cathode voltage decay time was reduced from 80~130 ms to 50~60 ns, the impact on the electron-optical systems by cathode voltage decay time was reduced, and the screen brightness decay time was reduced from 12~26 ms to 3~4 ms, when the outside light conditions was greater than 10－4 lx. The results prove that this method can effectively reduce the image intensifier cathode voltage decay time and screen brightness decay time and be used as reference scheme for improving this kind of camera still-picture quality.