Abstract: The study on the radiation resistance of complementary metal oxide semiconductor (CMOS) active pixel sensor (APS) digital module are presented, and a shielding structure has been designed and manufactured with the help of Monte Carlo simulation software. Shielding performance, operating life and damage modes of sensor modules have been analyzed. The result shows that with the shielding, the operating life of APS almost doubled. The irradiation dose rate is about 1/3 times of that without shielding when the main board is shielded, but the service life of the main board is only increased by 1 times after shielding. This may be originated from the differences in the radiation resistance and total ionizing dose of the devices on the module. The dark current is almost unchanged when the total dose is less than 50 Gy, and the dark current of all pixels in the sensors increases gradually when the total dose is greater than 150Gy.