The surface treatment is the beginning of the manufacturing process of HgCdTe infrared detector chip， and its quality will directly affect the yield of the chip. The mechanisms of four typical surface anomalies in the HgCdTe surface treatment process were explored using metallographic microscope， scanning electron microscope （SEM） and X-ray photoelectron spectroscopy （XPS） analysis methods， and the corresponding control measures are proposed. The water mark defect is triggered by oxygen absorption corrosion， and this defect can be controlled by rapidly drying the HgCdTe surface with a stable nitrogen gas flow. The staining is induced by the corrosive liquid unevenly diluted or contaminated by impurities such as water. To reduce the probability of staining， the contamination should be strictly avoided in the process， and the surface should be quickly rinsed after corrosion finish. The round spot originates from the adsorption of the cleaning solution at the material defect， which can be controlled via using isopropanol to soak the HgCdTe before drying. When toluene is in direct contact with HgCdTe， the surface roughness of HgCdTe will increase， thus this direct contact should be restricted.