In accordance with the icing problem of helicopter rotor blade, the aerodynamic characteristics of threedimensional rotor blade before and after iceup are studied. Based on the multiple reference frame model, a threedimensional numerical simulation method of rotor blade icing is established. The air flow field calculation, droplet impact characteristics calculation, ice accretion calculation and geometric model reconstruction are introduced among them. Taking CT rotor blade as a model, the influence of icing on the aerodynamic characteristics of CT rotor blade is calculated and analyzed. The results show that the lift of rotor blade decreases, the drag increases, and the hovering performance decreases obviously after iceup. The ice accretion damage to the original aerodynamic shape of the blade section results in the generation of vortices and the deterioration of aerodynamic characteristics.