Ducted propeller design requires a long time for the complexity of the mutual interaction between duct and propeller. A simple method was proposed for the purpose of designing the blade geometry during ducted propeller preliminary design stage in this paper. The mass flow through the propeller disk was calculated using the momentum theory and the incremental differential pressure before and after the propeller disk was estimated by applying the engineering experience. After the two steps, the blade primary geometry was designed in the basis of blade element theory. To verify feasibility of this method, the paper manufactured the blade and duct, and tested them in wind tunnel .The result shows that the design value approximates to the wind tunnel experimental results, which illustrates that the method is useful and effective. This method can accelerate ducted propeller design procedure.