Abstract: The hypobaric environment on Mars creates the condition for the aircraft to be used in the Mars explorations. The four-rotor aircraft will be a potential choice in the Mars aircraft investigation because of its simple structure and high reliability, besides, it can also hover in the air, and be able to takeoff and land repeatedly. This paper focuses on the propulsion technology for the Mars four-rotor aircraft, and a 2D-CFD model is established of its propellers. The relationship of the blade inclination, the rotation speed, and the radius with the blade lift is analyzed by the model. The preliminary design of propellers is made based on this relationship. By tests in thin atmosphere, the thrust of propellers is obtained which agrees with the numerical simulation. The results of this paper can provide a theoretical basis for the further design of the dynamic system of the Mars UAV (unmanned aerial vehicle) with four-rotor propellers.