Abstract: Fuel corrosion anomaly caused by CILC（crud induced localized corrosion） is one of the important reasons for fuel failure. Under the combination of primary water chemistry,reactor operating mode, exchange of system equipment, fuel design and fuel management,corrosion products（also called “crud”） released from primary system can be deposited on the fuel cladding surface in the upper core, and lots of the deposited corrosion products can cause the localized temperature arising on the fuel cladding surface, and then can induce cladding corrosion accelerated, and can even lead to the fuel failure. In this paper, the corrosion-scaling mechanism of fuel cladding is studied and the influencing factors are determined, which lays a foundation for the establishment of corrosion-scaling model, and is of great significance to the optimization of corrosion model in the comprehensive performance analysis of fuel rods.