Abstract: High strength steel 18CrNiMo7-6 is prone to grinding burns in grinding process.In order to reduce the occurrence of such burns, under the condition of dry grinding experiment, the grinding test of CBN grinding wheel was designed,and the surface temperature of the workpiece during grinding was measured by an artificial thermocouple. Th e influence of grinding depth, feed speed and grinding wheel speed on the workpiece grinding burn was studied by test. The changes of microstructure and microhardness of grinding burn were analyzed by using the method of microhardness and microstructural staining. The mechanism of grinding burn and the change of grinding burn depth of 18CrNiMo7-6 steel were studied. The results show that after grinding the burn layer, the microstructure changes obviously, and the tempering burn layer depth is 40-80 μm, and with the increase of depth from the surface, the hardness gradually restores to the original matrix hardness.