To enhance the propulsive efficiency of ducted propeller for better endurance of underwater-vehicle, 19A/Ka4 series ducted propeller is studied through numerical simulation to analyze the factors of the duct and blade on the hydrodynamic performance by change the such parameter such as length-diameter ratio, diameter ratio, blade area ratio and pitch ratio under different mesh models. It is discovered that the length-diameter ratio has almost no influence of the open water performance, though, the cavitation performance is better with the increase of length-diameter ratio. The lesser duct diameter ratio and blade area ratio will increase the efficiency, and accordingly, the thrust coefficient and torque coefficient will decrease. The influence of the pitch ratio on ducted propeller is similar to the conventional propeller, with the increase of pitch ratio, the peak efficiency will increase until to a constant value. Based on aforementioned research in a specified range of blade area ratio and diameter ratio, it is found that the minimum blade area ratio and minor diameter ratio will generate the extreme efficiency.