Abstract: The new type hybrid power Unmanned Aerial Vehicle(UAV) can fly at low altitude. The airframe related components mainly include airbag, ducted-fan and pull propellers. The UAV have the advantage of conveniently taking off and landing, safety, high efficiency and low cost, so that can be applied to fields of airborne geophysical prospecting, air transport, aerial observation, agriculture and forestry, air goods transportation and earthquake relief, etc. Based on the overall scheme of this new type UAV, the structural parameters of the rotor and ducted body were designed and optimized in this paper. FLUENT software was mainly used to carry on numerical simulation of ducted-fan model. Through the contrastive analysis of the results, the optimal structure parameters can be obtained. the gap between the tip of paddle and duct δ is 4 mm, the duct height H is 240 mm, the rotor disc position h is 80 mm, the ducted cone angle β is 5°.