This study deals with fretting wear behavior of 40CrNiMoA steel on a SRVⅣoscillating friction and wear tester. The results indicate that with the frequency and load increasing, both the friction coefficient and fretting wear volume increase. With the amplitude increasing, the fretting wear volume increased too, but the effect of amplitude on friction coefficient was not simple positive correlation according to the experimental results. Meanwhile, the fretting wear mechanism is directly related to test frequency, load and amplitude. When they are small, the main fretting wear mechanism is abrasive wear, with these test parameters increasing, the main fretting wear mechanism turns to a combination of abrasive wear and adhesion wear. Based on the experimental results, the anti-fretting wear measures of steel worm gear pairs used in mechanical tracked regulator of tracked vehicle are discussed.