The structural configuration of diagonal steel reinforcement to enhance shear resistance and flexibility for coupling beams has been well-established in numerous studies by Paulay and other researchers worldwide. When integrated into the load-resisting system of a semi-enclosed core structure, this configuration theoretically enhances the torsional resistance of the core compared to cases where coupling beams are conventionally designed or designed with limited load-bearing capacity. However, the specific role of diagonal steel reinforcement in coupling beams regarding the torsional resistance of the semi-enclosed core needs to be evaluated through core performance parameters such as torsional moment capacity and reduction in core twist angle. This paper employs the finite element method, incrementally increasing lateral loads, utilizing coupling beam models incorporating diagonal reinforcement and shell models for wall panels to analyze a typical core structure scenario with various coupling beam configurations incorporating different ratios of diagonal reinforcement. The analysis results are compared to elucidate the influence of diagonal steel reinforcement in coupling beams on the torsional behavior of multi-story reinforced concrete core structures.