To investigate the mechanism of the propeller slipstream influence on the aerodynamic performance of the submerged inlet, a systematical numerical method is developed to simulating the slipstream and inner flow of oil radiator for a certain turboprop aircraft. The aerodynamic characteristic of the submerged inlet of the oil radiator within the propeller slipstream is deeply analyzed. Moreover, several vortex generators are designed to control the flow around inlet of the oil radiator to increase the flow rate affected by the inhaled low energy flow of the boundary layer in the inlet. The results indicate that, the calculating data agree well with those of test by using the numerical method, and the reasonable vortex generator can effectively improve the flow of the submerged inlet by increasing the flow rate with 12%.