To mitigate the total pressure distortion index and swirl distortion index at the Aerodynamic Interface Plane (AIP) of a hefty deflection S-shaped inlet and enhance its performance, this study explores the incorporation of precisely angled deflectors positioned before the first bend of the inlet. A combination of numerical simulations and experimental validations is utilized to examine the performance variations of the double 90-degree S-shaped inlet. This analysis assesses the effects of incorporating deflectors compared to scenarios without them. The results indicate that the geometric configuration of the large-deflection S-shaped inlet is prone to significant AIP total pressure distortion. However, introducing deflectors markedly reduces the total pressure non-uniformity in the AIP and optimizes swirl flow distribution. The quantitative analysis demonstrates a reduction of 35% in the total pressure distortion index. Additionally, there is a 33.6% decrease in the swirl distortion index observed at a flow rate of 0.82 kg/s. This approach provides a novel strategy for optimizing the design of a large-deflection S-shaped inlet. The findings conclude that deflectors can substantially enhance the performance of a large-deflection S-shaped inlet and offer a specific solution for related inlet design challenges.