Abstract: The intergranular oxidation behavior of 15CrMo steel at different heating temperatures was studied by thermogravimetric analysis, scanning electron microscopy and electron probe analysis. The results show that with the increase of heating temperature, the oxide scale thickness of the outer layer of 15CrMo steel increased gradually, and the intergranular oxidation depth increased first and then decreased. The nose tip temperature of 15CrMo steel for intergranular oxidation was 850℃, and the depth of intergranular oxidation was about 12. 9 μm. In the intergranular oxidation, Si, Mn and Cr element were preferentially enriched, and Mo element could only diffused to the interface near the matrix. It was suggested that the formation of intergranular oxidation should be controlled by appropriately reducing the heating temperature.