We propose a high speed digital smart image sensor on which A/D conversion circuits and digital processing circuits of image compression are integrated. By on-sensor image compression, the proposed sensor can overcome a communication bottle neck between a sensor and peripherals that is one of the most serious problems for achieving high frame rates. The compression method uses the correlation between two consecutive frames. It has some compression modes by controlling spatial and temporal resolutions. In this paper, the algorithm of on-sensor-compression is explained and some experimental results are shown. Finally, we show the design of new digital smart sensor.