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The effects of normal load (60 N, 40 N and 20 N) on the tangential fretting wear properties of the TC21 titanium alloy and plasma electrolytic oxidation (PEO) coatings were investigated under displacement amplitudes of 50 μm and 150 μm with a ball-on-plate contact configuration. The results showed that with increase of the displacement amplitude and decrease of the normal load, the fretting wear regime changed from partial slip regime to slip regime. In partial slip regime, the widths of the wear tracks along the fretting direction decreased with the decreasing normal load. Although there was no significant material loss, the extent of micro-cracks initiation and propagation in the micro-slip zone of the TC21 titanium alloy deepened with the decreasing normal load. However, the fretting only played a smooth effect on the PEO coatings. In slip regime, the widths of the wear tracks along the fretting direction increased with the decreasing normal load. There existed local wear in both materials, and the wear degree increased with the increasing amplitude and decreasing normal load. The maximum wear depth of the PEO coatings was shallower than that of the TC21 titanium alloy, which proved that they could improve the fretting wear resistance.