A ducted fan has many advantages comparing to an open rotor. Theoretically, the ducted fan minimizes a formation of the tip vortices to obtain higher thrust. Therefore, many researchers have done the trade off studies for the parameters of ducted fan shapes. In the present study, an interaction between a duct rotor and parametric effects of the tip clearance of ducted fan on the aerodynamic performances are analyzed. To simplify the computational analysis, a horizontally expanded ducted fan shape is utilized. The results show that the overall aerodynamic performances are increased as tip clearance decreased.