A series of variable-area photodiode devices with different P/A ratio were prepared by different passivation processes. The relationship between R0A of the devices and 1 000/T was analyzed in temperature range 77～147 K. The result shows that the dark current of device is dominated by diffusion current in the temperature range. The distribution of R0A was studied. The bulk defects and non-uniformity in HgCdTe thin films have an important influence on the performance of the device at 77 K. Due to the increase of the bulk diffusion current at 127 K, the effect of the defect on the device is significantly weakened. R0A values of the devices decrease with the increase of P/A ratio, which indicates that the surface passivation has an important effect on the device at 77 K and 127 K. The relationship between R0A of the devices and P/A ratio was analyzed based on Vishnu Gopal model. The surface leakage of the device is confirmed, and the effect of surface passivation on the performance of the device is effectively reduced by the improvement of the passivation process.