The subject of this study is the efficiency of the propeller of an unmanned aerial vehicle. The object is the propeller of an unmanned aerial vehicle. The purpose of this work was to assess the influence of the shape and number of blades on the efficiency of the propeller of an unmanned aerial vehicle. To achieve this purpose, the following tasks were solved: obtain the dependence of efficiency on the rotation speed of seven two-blade propellers with different blade shapes; obtain the dependence of efficiency on the rotation speed of propellers with two, three, four, and five blades. The study of the flow in the propeller of an unmanned aerial vehicle was carried out using a numerical experiment. The Navier-Stokes equations were closed by the SST turbulence model. The efficiency was calculated based on the aerodynamic calculation of the propeller. The rotation speed range varied from 3000 rpm. up to 11000 rpm. Results: An assessment of the influence of the shape and number of blades on the efficiency of the UAV propellers and the distribution of thrust force over the surface of the blade is presented. It has been shown that the shape and number of blades influence propeller efficiency. All seven propellers with different blade shapes at certain rotation speeds had an efficiency above 0.9. At the minimum tested speed of 3000 rpm. the efficiency of all two-blade propellers had the lowest values, ranging from 0.2 to 0.78. As the engine rotor speed increases, the efficiency of the propellers gradually increases; the maximum efficiency is observed at rotation speeds of 6000–10,000 rpm. Visualization of the thrust force on the surface of the blades of the two-bladed propellers showed that the shape of the blades also affects the generation of thrust. During a two-stage study, the shape and number of UAV propeller blades were substantiated. The resulting three-bladed propeller has an efficiency ranging from 0.63 to 0.98 in the rotational speed range from 3000 rpm. up to 11000 rpm. The scientific novelty and practical significance of the conducted research lies in the fact that new data were obtained on the influence of the shape and number of propeller blades of an unmanned aerial vehicle on the propeller efficiency. The obtained data can be used to create and optimize the parameters of unmanned aerial vehicle propellers.