Abstract: By analyzing the effects of matrix hardness,tempered martensite quantity,nitriding temperature,nitrogen potential value,and gas exchange rate on nitriding performance of 40CrNiMoA steel,the study shows that the depth of the hardened layer/498HV1 increases with the increase of matrix hardness,tempering martensite quantity,decreasing nitriding temperature,and increasing nitrogen potential value and gas exchange rate.Gas nitriding of 40CrNiMoA steel can achieve a surface hardness of 600HV1 to 635HV1,while meeting the technical requirements of 498HV1 at a depth of 0.52mm.