Based on COMSOL, the model of cycloid pump was established, the dynamic grid technology was used in the rotating domain, and the uniform pair method was used in the dynamic and static regions to realize data transmission. After setting the corresponding boundary conditions, the CFD simulation of the pump was carried out, and the feasibility of the simulation model was verified by experiments. The flow field characteristics of the cycloidal pump under different temperatures were compared. The results show that the error between test and simulation is slightly more than 5%, so the simulation model is feasible. The outlet flow and pressure characteristics of oil at different temperatures were compared. The results show that with the decrease of oil viscosity, the mean value of outlet flow of the cycloidal pump decreases, and the flow pulsation rate increases; the mean value of outlet pressure of cycloidal pump changes little, but the pressure pulsation rate increases significantly. The cross section of cycloidal pump rotating area under different temperatures were analyzed. The results show that the decrease of oil viscosity makes the oil fluidity better, resulting in the lower negative pressure in the oil suction area, and the increase of radial and axial leakage in the oil discharge area, so the pump outlet flow is reduced. The research results provide reference for other pumps simulation.