In this paper, the growth conditions of highly crystallographic CdTe passivation layer are optimized to regulate the density of the film. The surface morphology, microstructure and optical properties of CdTe passivation layer are thoroughly analyzed by SEM and ellipsometry, and the optimal dense growth conditions are obtained. The interface electrical properties between CdTe films and HgCdTe with different densities and their effects on the properties of photodiodes are systematically studied by C-V and I-V characterization methods. The results show that the density of CdTe passivation layer is the best when the sputtering power is 200 W, which effectively improve the interface electrical properties between the passivation layer and HgCdTe. The MIS devices prepared by this power have a lower interface fixed charge density of 1.21×10¹¹ cm^-2 and a slower interface state density of 1.26×10¹¹ cm^-2. Moreover, diode devices prepared by this power can effectively suppress the surface leakage phenomenon of the device.