Abstract: Significant lateral forces induced by strong propeller slipstreams during low-speed takeoff pose a safety threat to multi-engine propeller aircraft. Effective suppression of these forces is crucial. This study investigates the generation mechanism of lateral forces on the engine nacelle under high-lift and high-thrust conditions, as well as the suppression mechanism of a nacelle strake, using numerical simulations. The effects of key parameters, including the strake’s circumferential position and height, on lateral force reduction are analyzed. Results indicate that the strake effectively suppresses the propeller-induced circulation and increases the pressure on the upstream side of the nacelle, thereby significantly reducing the lateral force. The optimal suppression effect is achieved at a circumferential installation position of 50°. At this position, the lateral force coefficient is reduced by 79% at a 4° angle of attack and by 63% at an 8° angle of attack. Shortening the strake—either by retracting the leading edge or advancing the trailing edge—diminishes its effectiveness. However, retracting the leading edge has a relatively minor impact: when the leading edge is retracted by 0.4 m, the lateral force coefficient can still be reduced by 75% compared to the configuration without a strake. In addition, the height of the strake is found to have a notable influence on lateral force suppression.