Abstract: The fretting wear behaviors of AZ91D and AM60B magnesium alloys self-paired in a plane-on-ball configuration were investigated using a universal material tester of highly accurate displacement control. The effects of the number of cycle, amplitude of slip, normal load, and frequency on the friction and wear properties of the Mg alloys were analyzed. The morphologies of the fretted surfaces and wear debris of the Mg alloys were observed using a scanning electron microscope. The results indicated that the two die cast magnesium alloys had fretting wear mechanisms including adhesion wear, surface fatigue wear, abrasive wear, and oxidation wear. The fretting wear behaviors of the two Mg alloys were closely dependent on the testing parameters such as frequency, slip amplitude, and normal load, while the Mg alloy AZ91D showed better fretting wear resistance than the Mg alloy AM60B. This could be attributed to the larger plasticity of the AM60B than the AZ91D. In other words, it needed much more time for the AM60B of larger plasticity to form a stable third-body layer capable of decreasing wear during the fretting process under the same test conditions, therefore AM60B had poorer fretting wear resistance than AZ91D.