<p>The normal stress magnitude, stress gradient, and tangential stress at the coating-substrate interface of gear systems are key metrics for assessing interfacial bonding strength. Because the reinforced coating is extremely thin and the interfacial stress field is highly complex, conventional numerical methods often exhibit poor convergence and low computational efficiency when analyzing discontinuous interfacial fields. To address these limitations, this study develops a novel, accurate, and efficient calculation method based on interfacial and contact mechanics. An interfacial mechanics analysis model under concentrated contact loading is established to predict the interfacial stress distribution in coating-reinforced gear systems. By varying coating thickness and the elastic modulus ratio between coating and substrate, we systematically investigate the distribution patterns and evolution of interfacial stresses under concentrated loading and elucidate how these parameters influence the interfacial stress field. Finally, detailed numerical experiments based on the full field analytical solution are presented and compared with finite element simulations to verify the accuracy and effectiveness of the proposed method. This study provides a necessary theoretical basis for the detailed design, strength testing, and reliability evaluation of gear coating structures in practical engineering applications and holds significant importance.</p>