This article focuses on the problem of high cycle fatigue （HCF） failure of gas turbine blades caused by hot corrosion. NaCl+Na₂SO₄ salt mixture is used for hot corrosion of K444 alloy for turbine blades. The microstructure， composition， and hardness of the hot corrosion layer are studied using SEM， EDS， and nanoindentation. The effect of hot corrosion on the HCF strength of K444 alloy is studied based on the stepwise loading method. The research results indicate that hot corrosion causes oxidation and sulfurization of the K444 alloy， with the sulfurization layer located below the oxidation layer， and there is a γ' depletion zone in the matrix adjacent to the sulfurization layer. As the duration of hot corrosion increases， the oxide layer gradually thickens， and the thickness of the sulfide layer shows a trend of first increasing and then decreasing. The hardness order obtained from nanoindentation analysis is the oxide layer>matrix>sulfide layer. Hot corrosion accelerates the initiation of fatigue cracks in K444 alloy， resulting in a decrease of fatigue strength of K444 alloy notched specimens by 9.68% — 23.97%.