Abstract: In order to study the effect of bonding proportion on behaviors of cemented sand combined with particle breakage effect, the conception of particle breakage was introduced and cemented sand behaviors were studied by numerical simulation with the built contact bond model in PFC3D. A series of triaxial compression tests on cemented sand of different bond proportions were carried out. Then, the simulated results were compared with the test results on artificially cemented sand from laboratory tests. The micromechanical responses were analyzed by numerical simulation. Results show that the discrete element method model is able to capture the main mechanical behaviors of cemented sand. Compared with uncemented sand, cemented sand has greater strength, and shows strain-softening in stress-strain curve and transition from compaction to shear-dilation in volumetric strain. The macromechanical responses of cemented sand (stress-strain relationship and dilatancy) are closely associated with the micromechanical responses. Bond breakage ratio and rate are low at the initial loading stage and then rapidly increase after yielding point. Bond breakage rate peaks at peak strength and deceases afterward, while the bond breakage ratio increases slowly and become stable. A sample with lower bond proportion and bond strength has higher bond breakage ratio and rate. High bond proportion leads to more broken particles and dilation in volume. When bond proportions are 0 and 100% respectively, particle breakage ratio increases from 1.13% to 10.96%. In contrast to uncemented sand, the bond develops the shear band, and larger and more concentrated contact force.