The surface sulfide treatment characterization of HgCdTe has been studied by XPS. Sulfide treatment after Br2-C2H5OH etching can remove the oxide of the surface of HgCdTe, and decrease Te enriched. Then, in order to improve the performance of the photodiodes, the ZnS layer deposited after sulfidation is used to passivate the photodiode. The measurement shows that the photodiodes can low the dark current, and increase the operating voltage.