Abstract: The tangential fretting wear tests were conducted on AZ31B magnesium alloy with a self-designed fretting wear tester by contact form of ball against plane, the fretting wear behavior of AZ31B magnesium alloy at 20, 100, 200, 300℃ was studied, and the wear mechanism and the tribo-oxidation effect were analyzed. The results show that the fretting of magnesium alloy took place by means of sliding at different testing temperatures. With the increase of testing temperature, the friction factor in the ascending stage increased, and the number of cycles when friction factor reached peak value and stable stage decreased. The wear volume of AZ31B magnesium alloy and total wear volume of friction pair both decreased first and then increased with the increase of testing temperature, and the wear volume of AZ31B magnesium alloy was the smallest at 200℃. The tribo-oxidation on wear scar surface of AZ31B magnesium alloy played a key role in the fretting wear process. The iron oxide transfer layer was formed on the wear scar surface of AZ31B magnesium alloy when the testing temperature was below 200℃; the wear volume decreased with the increase of testing temperature. The iron oxide transfer layer was destroyed at 300℃ and the wear volume increased.