In order to reduce the structural weight of aircraft, structural optimization design for a Lift-fan UAV with ANSYS parameter design language(APDL) is carried on in this paper. Considering the special structural characteristics and flight conditions of the lift-fan UAV, the geometry optimization of the components was mainly conducted. At first, establishing the parametric analysis procedures for the structural optimization design of the lift-fan UAV was necessary. According to this procedures, the parametric modeling, loading and solving of the lift fan UAV were achieved. Then, using ANSYS optimization module was to complete the structural optimization. Finally, the results of the optimization were analyzed effectively. It shows that the method is rationality and validity.