The wake effect of the upstream wind turbine reduces the incoming wind speed and the output power of the downstream wind turbine. In order to increase the total power of the wind turbines, the NREL wind turbine aerodynamic analysis model was first constructed based on CATIA software and Fluent software to calculate the surface pressure coefficient of the wind turbine blades and the output power of the wind turbine at a constant wind speed compared with the American wind tunnel experiment to verify the accuracy of the aerodynamic analysis model of the NREL wind turbine. Subsequently, the effects of the tandem spacing and the size of the rotor on the thrust, torque and power of the wind turbine were calculated and analyzed. The study showed that the wake effect of the front rotor is weakened and the power of the rear rotor is gradually recovered with the increasing in spacing.