Purpose: Current simulations mainly apply the principal strain or the equivalent strain to judge the mechanical state of the element in the finite element model and then perform the fracture simulation in the cortical bone. However, there is no general strain judging criterion for accurately simulating the cortical bone fracture, so which strain is more suitable for determining the element mechanical state and performing the fracture is not clear now. Methods: This study was intended to perform the fracture simulation in the cortical bone structure under compression load based on the continuum damage mechanics theory to explore the suitable strain judging criterion in the compressive fracture condition. The principal strain and the equivalent strain were used to judge the element mechanical state in the finite element model and perform the fracture simulation. Then, the simulation results were compared with the corresponding experimental data to determine the prediction accuracy using the two judging strains. Results: The fracture time in the simulation using the equivalent strain was remarkably later than that using the principal strain, and the simulation results obtained by applying the principal strain were closer to the animal experimental values than that obtained using the equivalent strain. Conclusions: The application of the principal strain to determine the damage and failure state of the element in the finite element model to perform fracture simulation was more accurate under the compression load. In this study, a feasible numerical simulation method was established to simulate the fracture of cortical bone under compression load, which could provide theoretical basis for improving the fracture prediction accuracy in clinic.