The propeller performance of small loitering munition is easily affected by the smaller blade size and lager hub ratio. A loitering munition encountered the problems of propeller speed is too high， and the endurance is not enough， the propeller wind tunnel test， the calculation results and flight performance are different. Aiming at the problem of inconsistent calculation results， the numerical simulation of the experimental subject was carried out. The result shows that the propeller hub produces a large negative thrust and torque， which is the most important factor leading to a significant decrease in propeller efficiency and increase in propeller speed. According to the calculation results， the formula of the hub thrust and torque correction and the propeller optimization design are given. In view of the large difference between the wind tunnel test efficiency value and flight performance， the propulsion system wind tunnel test was carried out， the problem of incoming flow interference is solved and accurate experimental results are obtained. In order to improve propeller efficiency， a propeller calculation model is derived based on propeller vortex theory， the optimization design of propeller aerodynamic profile is carried out by using genetic algorithm toolbox， with the efficiency of propeller at cruise as objective， the thrust and maximum counter torque in climb as constraints. The design results are verified by the wind tunnel test of the propulsion system. Experimental results show that the optimized design is effective， and the propeller efficiency is increased by 17.2% at cruise.