Abstract: This study addresses the scientific and engineering problem of analyzing interlaminar mechanical behavior in the R-region of composite L-shaped curved laminates by proposing an efficient and accurate theoretical model for predicting stress fields and failure behavior in this region. The model achieves precise prediction of interlaminar stresses in the R-region based on higher-order theory, while classical laminate theory is integrated to further establish a predictive method for intralaminar stresses. Additionally, an interlaminar-intralaminar stress coupling coefficient is introduced to account for the influence of intralaminar stresses on interlaminar failure behavior, thereby improving existing interlaminar failure criteria. The accuracy of the theoretical model is systematically validated using detailed finite element simulations. Results demonstrate that the stress distributions obtained from finite element analysis, after eliminating free-edge effects, align well with theoretical predictions, confirming the model’s accuracy. For failure behavior validation, both experimental tests and finite element simulations are employed to assess critical failure loads and failure modes. The theoretical predictions show strong agreement with experimental and numerical results in terms of critical failure loads and failure patterns, further verifying the model’s reliability. The proposed theoretical model combines high computational efficiency with superior predictive accuracy, providing a reliable analytical tool for the structural design and performance evaluation of composite L-shaped curved laminates.