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The intrinsic trade-off between hardness and fracture toughness in carbide ceramics poses a severe challenge to their broader applications in advanced manufacturing. While grain refinement is known to enhance both properties, the underlying mechanisms through which microstructural factors (including grain size, grain orientation, and grain boundaries) govern crack propagation remain insufficiently understood. In this study, the fracture energy dissipation-based evaluation model within the phase-field framework was established to visualize fracture resistance in binderless WC cemented carbides. By integrating this model with experimental characterization, the influence of grain-scale microstructural factors on crack propagation was systematically investigated. The results reveal that the orientation-dependent fracture resistance of WC grains, grain boundary inclination, and especially grain size strongly influence the fracture mode and energy dissipation. Notably, grain refinement induces the increasement of transgranular fracture proportion, significantly increasing fracture energy dissipation. The binderless WC cemented carbide with finer grains (0.96 ± 0.01 μm) achieves a balanced combination of high fracture toughness (6.23 ± 0.16 ) and hardness (2231.19 ± 37.96 ). Both experimental and simulation results confirm that WC grain refinement is an effective strategy for improving fracture resistance, thereby validating the effectiveness of the fracture energy dissipation assessment model. The presently developed methodology provides critical insights into microstructure–crack interactions and opens new avenues for the microstructural design of high-toughness carbide ceramics.