In this paper, an improved AE system for digital still camera is proposed. AE system is auto exposure system to maintain optimized brightness of output image. But there is limitation for mobile devices to get high quality image with the conventional AE algorithm, because of organizational restriction of system. The conventional research has been studied only electronic shutter and AGC on the AE algorithm. In this paper, we suggest new AE algorithm included target setting, frame delay, Gamma Correction as well as electronic shutter and AGC to get high quality image. The proposed algorithm show improved result at control speed and ability of luminance expression.