In order to analyze the effect of fan rotor blade leading edge erosion on the aerodynamic characteristics of the compression system for different internal and external culverting conditions, multilevel cascade calculations were used to investigate the changes in the aerodynamic characteristics of the compression system of a certain type of engine with large culverting ratio. The results show that the total pressure ratio, isentropic efficiency and channel flow rate of the engine compression system after leading edge erosion relatively decrease by 0.18%, 0.879% and 0.972%, respectively, under the peak efficiency point working condition. For fan rotor blades, leading edge erosion leads to a decrease in the slope of the surface static pressure coefficient curve in the axial 0 ~ 24% interval of the surface static pressure coefficient curve at the height of 95% of the blades under near-surge point conditions in the outer culvert channel, with a decrease in static pressure, and an increase in the slope in the axial 24% ~ 40% interval, which reduces the loading of the blade, reduces the pressurizing capacity, and moves the surge wave forward. In addition, leading edge erosion increases the angle of attack of the overall fan blade at the near-surge point of the outer culvert by about 2°, resulting in changes in blade aerodynamic efficiency and stall margin, which deviates from the original blade design.