Abstract: High entropy alloys have attracted much attention in the coating industry due to their excellent mechanical properties and corrosion resistance. However, as the application of high-entropy alloys continues to expand, the corrosion environments have become more diverse and complex. In order to investigate the corrosion condition of CoCrFeNiMo_0.2high entropy alloy under different temperatures（25 ℃, 40 ℃, 55 ℃） and different ion types（3.5 wt%NaCl and 3.5 wt%NaCl+0.1 mol/L NaOH）, the corrosion conditions were analysed by electrochemical testing, XPS testing of passivation film of the alloy coatings, as well as SEM/EDS analysis of corrosion morphology of the coatings. The corrosion condition of the alloy coating was analysed by electrochemical tests, XPS tests of passivation film and SEM/EDS inspection of the coating morphology. The results show that the CoCrFeNiMo_0.2high entropy alloy has different degrees of passivation behaviour in both solutions at different temperatures, and the corrosion resistance of the CoCrFeNiMo_0.2high entropy alloy has been improved in the composite environment containing OH^-and Cl^-, but the overall corrosion rate is still increased with the increase of temperature. The change of decrease of CoCrFeNiMo_0.2high entropy alloy in the two solutions in the corrosion resistance performance with the increase in temperature is due to the increase in temperature make the corrosion resistance element Mo oxide content reduces, but also accelerates the solution of the metal ions and chloride ions reaction, which leads to the generation of pitting corrosion, the coating corrosion resistance performance decreases.