Fretting wear tests of Zircaloy-4 alloy against Inconel 718 alloy were conducted on a fretting wear rig. The contact state and fretting running characteristics of Zircaloy-4 alloy were investigated. The running condition fretting map of Zircaloy-4 alloy presents three regimes, namely, partial slip regime, mixed slip regime, and gross slip regime. Slight degradation was observed in the partial slip regime. In the mixed slip regime, adhesive wear of the stick zone and oxidation wear of the slip zone are the main damage mechanisms, and cracking was observed at the stick-slip boundary. Severe material detachment due to wear is predominant in the gross slip regime, and the main damage mechanisms are adhesion, plastic deformation, surface fatigue, frictional oxidation and abrasion. •The RCFM of Zircaloy-4 alloy presents three regimes: partial slip regime, mixed fretting regime, and gross slip regime.•The MRFM of Zircaloy-4 alloy presents three domains: slight degradation, adhesion and cracking, and severe wear.•The sliding state is closely related to the tangential force of the contact surface.•The MSR was the most critical for crack nucleation and propagation.•Wear accompanied by severe oxidation is the main damage mechanism in the GSR.