Aiming at the problem that the infrared detector is degraded by the high-energy particle irradiation in the space application, the effect of γ-ray on the dark current of the medium-wave HgCdTe photovoltaic device was studied. The HgCdTe device was irradiated with 60Co-γ rays at room temperature and 77 K. After the irradiation test, the low temperature irradiated device was subjected to 77 K low temperature annealing and room temperature annealing. By comparing the I-V characteristics, R-V characteristics and zero-bias dynamic resistance R0 parameters of the device before and after irradiation, the influence mechanism of γ-irradiation on the dark current of the HgCdTe device was analyzed. The test results show that the dark current of the device does not show obvious degradation after irradiation at room temperature under the total dose of 7 mrad(Si). Under 77 K temperature irradiation conditions, the dark current of the device increases with the dose, and the dark current degradation amplitude is related to the bias during the irradiation test. Studies have shown that the degradation of dark current was caused by gamma irradiation causing ionization damage in the device, resulting in an increase in the interface state and hole trap charge density in the device's CdTe passivation layer.