Background <p>The fracture properties of PBX substantially affect its structural and functional reliability.</p> Objective <p>This paper investigates the quasi-static and fatigue fracture behavior of HMX-based PBX specimens containing prefabricated cracks.</p> Methods <p>Semi-circular bending (SCB) tests were performed under quasi-static and fatigue loading. Digital image correlation was used to examine the deformation field near crack initiation, while crack propagation gauges were used to measure unstable crack propagation velocity.</p> Results <p>Under quasi-static loading, crack initiation occurred near the maximum load. The fracture toughness at 35&#xa0;°C was 0.314&#xa0;MPa·m^1/2. Under fatigue loading, the fracture process exhibited three stages: rapid damage accumulation, stable damage development, and final crack initiation followed by unstable propagation. The first two stages accounted for more than 95% of the fatigue life. The fatigue limit of the maximum stress intensity factor at 35&#xa0;°C for 1 × 10⁶ cycles was 0.264&#xa0;MPa·m^1/2. The unstable crack propagation velocity under fatigue loading was lower than that under quasi-static loading, although both cases showed a similar slow–fast–slow propagation trend.</p> Conclusion <p>The results provide useful experimental data for understanding the fracture behavior of HMX-based PBX under quasi-static and fatigue loading conditions.</p>