To study the strength properties of Polymer bonded explosive (PBX) under compression -shear stress state, compression-shear test of PBX simulant was carried out by the experimental method of variable angle shear with loading angle θ 0°, 15°, 30°, 45°, 60°, 75°, 90°; The power function Mohr-Coulomb (M-C) criterion of PBX simulant was established, and compression strength under confining pressure was predicted. The mesoscopic failure characteristics of PBX simulant under compression-shear stress state were analyzed by SEM. The results showed that shear fracture pattern was along the compression-shear surface under loading angles 0°, 15°, 30° and 45°, and hybrid fracture pattern of shear and tension occurred under loading angles of 60°, 75° and 90°; For the shear fracture pattern, with the increase of compression stress, the shear strength of PBX simulant showed a trend of non-linear increase, and the mesoscopic damage would gradually develop from particle shear fracture and breakage to the formation and penetration of secondary cracks. The analysis found that the power function M-C criterion could well describe the trend that shear strength of PBX simulant increased nonlinearly with the increase of compression stress, and predict axial compression strength of PBX simulant under different confining pressure more accurately. The increase of internal friction resistance caused by the increase of compressive stress and the decrease of internal friction coefficient caused by particle breakage and secondary cracks are the important reasons for the non-linear increase of shear failure strength of PBX simulant with the increase of compression stress.