According to the application requirements of small satellite, mirco-and-nano-satellite, in this paper, the chip structure and key technologies of CMOS image sensors with radiation tolerant technology were studied. And mainly the technologies of row and column circuit, low noise readout, programmable gain amplifier and on chip ADC were analyzed and simulated. Simulations were performed on the key circuits and the whole chip layout was verified based on 0.35μm CMOS radiation tolerant technology. Test results show that this sensor presents such characteristics as high dynamic range, low noise and radiation tolerance. The noise is 42e- and the dynamic range is 69dB. The noise matches the requirements when the total dose irradiation is over 100krad(Si).