Abstract: The phase field method, recognized for its effectiveness in fracture analysis, particularly of isotropic and composite materials, remains a key research focus when considering the intricacies of fractures in anisotropic materials and their composites. In this study, a refined approach to decomposing elastic strain energy was presented. This method excludes the compressive volumetric strain energy influence on crack propagation and accounts for asymmetries in material constitutive relationships under tension and compression. Leveraging this, a tailored phase field analysis model for orthotropic material fractures was constructed. To validate the model's robustness and applicability, this work conducted analyses on unidirectional opening plates made of isotropic and orthotropic materials, focusing on tensile and shear boundary conditions. For composite plates with unidirectional fiber reinforcement, the Hashin criterion was incorporated to refine the quantification of damage-induced crack driving forces. This facilitated accurate simulations of tensile behavior in composite plates with varying carbon fiber orientations. Our findings demonstrate the profound capability of our theoretical framework in simulating crack propagation in anisotropic materials and unidirectional fiber-reinforced composites. The predicted crack propagation paths align with those from established models for both isotropic and orthotropic materials, attesting to the model's fidelity. Within composites, we observed a strong alignment between crack propagation and fiber orientation, highlighting a robust correlation between our predictions and experiment results.