<p>The elastic anisotropy of layered rocks has a significant impact on the accuracy of mode I fracture toughness testing, which is critical for the safety and design of underground engineering. This study presents a systematic comparison of the applicability of four calculation methods for determining the anisotropic rock fracture toughness of rock materials. The evaluation is based on fracture experiments conducted on semicircular bend (SCB) specimens under both symmetric and asymmetric loading conditions, supported by numerical simulations. The results indicate that traditional isotropic and anisotropic factor methods overestimate the mode I fracture toughness of coal. Furthermore, the crack deflection angle correction method underestimates the fracture toughness due to the influence of crack deflection effects. In contrast, the improved SCB test method, achieving pure mode I loading, demonstrates the highest accuracy among the evaluated approaches. Elastic anisotropy not only influences the loading parameters and principal stress direction of specimens but also intensifies its effects with increasing anisotropy degree, leading to complex anisotropic characteristics in fracture toughness and crack propagation. The improved SCB method, analyzed through the tangential stress ratio and energy release rate ratio, demonstrates superior applicability for investigating crack deflection behavior in layered rock formations. This research provides valuable theoretical guidance for the accurate determination and practical engineering application of fracture toughness in anisotropic layered rocks.</p>