The work aims to study the corrosion behavior of Tungsten alloy coating in the underground environment of Tahe oilfield (high temperature, peracidity and N2 injection). The underground environment of Tahe oilfield was simulated in high temperature and high pressure autoclave and the corrosion behavior of Tungsten alloy coating under simulated conditions was studied by weight loss measurement, coating thickness test, mircohardness test, SEM, EDS and XRD. Hardness of sample before corrosion was 825HV, while the hardness of all samples after corrosion could not be measured because of the collapse of indentation corners. In H2S dominated environment, the weight of samples increased obviously. When temperature reached 130 ℃, there was no stratified phenomenon on the coating, but the surface had corrosion products. Stratified phenomenon and bubbling obviously appeared on the coating at 200 ℃ and the bubbles broke out. Local corrosion was also observed on the surface and element S was detected in the local corrosion position by EDS test, indicating that S reacted with Fe to form iron sulfides. The weight of samples did not change significantly after corrosion at 160 ℃ in the H2S/CO2 and CO2 dominated environment and there was no weight loss, either, but light stratified phenomenon appeared on the surface. The weight and thickness of samples decreased significantly in the environment of N2 injection. The coating corrosion was mostly uniform and stratified phenomenon appeared in the coating as well. The coating became brittle after corrosion in all simulated environments. In the environment with high H2S and N2, Tungsten alloy coating has obvious stratified phenomenon, local corrosion and poor corrosion resistance, but shows slight stratified phenomenon in other environment.