Abstract: Fatigue damage often occurs in steel structures under cyclic loads. Due to the complexity of the structure and the composite nature of the loading form, the steel structure often produces I/II hybrid cracks, and fatigue crack repair has been a hot spot in the fatigue research of steel structure. Carbon fiber reinforced polymer composites (CFRP) have many advantages and good application prospects in the repair of steel structures. The current research mainly focuses on the repair of I-mode cracks, but there are much fewer investigations on the propagation and repair of I/II mixed mode cracks. With this aim, the current research status of crack propagation in steel under mixed modes is first reviewed in terms of the calculation methods of fatigue crack propagation, crack propagation rate, and equivalent stress strength factor. The current status of mixed mode crack propagation is emphasized, and the effects of factors such as CFRP base material properties, CFRP-steel interfacial bonding properties and different crack angles on the performance of mixed mode crack repair are analyzed. Based on the current research status, the application prospect and research focus of I-II mixed mode crack propagation of steel structures repaired with CFRP under fatigue loading are prospected.