Fretting wear caused by flow-induced vibration is the predominant cause of fuel cladding failure of pressurized water reactor (PWR). The Cr-coated Zr alloy is one of the most promising candidate materials for accident tolerant fuel, due to its outstanding high temperature oxidation resistance and corrosion resistance. However, research of fretting wear behavior and mechanism of Cr-coated Zr alloy cladding relatively little exists. In this paper, the fretting wear behavior and damage mechanism of Cr-coated and uncoated Zr-1Nb alloy cladding with AFA 3G grid under simulated PWR primary water environment were studied contrastively by 3D white light interferometer, scanning electron microscopy and energy disperspective spectroscopy. The results indicated that Cr coating can significantly improve the fretting wear resistance of Zr-1Nb alloy cladding. In addition, for cladding against dimple, the dominant wear mechanism of Zr-1Nb was delamination and abrasive. However, the main damage mechanism of Cr-coated Zr-1Nb was adhesive wear and materials transfer, due to higher surface hardness and formation of protective third body layer. For cladding against spring, the damage mechanism was delamination and adhesive wear for Zr-1Nb, while abrasive wear for Cr-coated Zr-1Nb.