Abstract: A Single Rotor(SR) ducted propeller and two Contra-Rotating(CR) ducted propellers with different pitch-of-ratios are designed on the basis of the cascade theory, and the numerical simulation of the flow field is carried out using commercial CFD software. The upstream rotor pitch ratios of the two CR ducted propellers are 1.451 and 2.108 respectively, and the pitch ratios of the downstream rotors are designed according to the principle of eliminating the swirl flow. The simulation results show that both the thrust coefficient and the torque coefficient of the CR ducted propellers are improved significantly with the increase of pitch ratio, while the efficiency increases slightly and the maximum efficiency point of the propeller is offset to the right. Compared to the SR propeller, the CR ducted propeller can maintain higher propulsive efficiency at a higher pitch ratio.