This paper presents a numerical study on the pullout behavior of the rockbolt grouted system. Among the complicated failure modes of the rockbolt grouted system, the crack of the grout is concerned here. A trilinear cohesive zone model(CZM) is used to simulate the interfacial behavior of rockbolt–grout interface;and a plastic damaged model is adopted for the grout materials. The feasibility of the numerical method is verified by comparing the calculated results with the test observations. The numerical results indicate that two types of cracks of the grout materials can be identified as the inclined crack and the horizontal crack. The inclined crack forms firstly and then the horizontal crack. Both cracks can reduce the interfacial shear stress and thus reduce the load transfer efficiency. Further analysis indicates that the crack of the gout material can induce the obvious drops of load capacity, which is not a safe failure mode. This study leads to a better understanding of the mechanism for rockbolt grouted system. Among the complicated failure modes of rockbolt grouted system, the crack of the grout is concerned here. A trilinear cohesive zone model (CZM) is used to simulate the interfacial behavior of rockbolt-grout interface; and a plastic damaged model is adopted for the grout materials. The feasibility of the numerical method is verified by comparing the calculated results with the test observations. The numerical results indicate that two types of cracks of the grout materials The inclined crack forms first and then the horizontal crack. Both inclined cracks forms the first and then the horizontal crack. Both cracks can reduce the interfacial shear stress and thus reduce the load transfer efficiency. Further analysis indicates that the crack of the gout material can induce the obvious drops of load capacity, which is not a safe failure mode. This study leads to a better understanding of the mec hanism for rockbolt grouted system.