Objective To explore a suitable judging criterion of the strain under compressive fracture condition. Methods Fracture simulation of cortical bone structure under compression loads was performed based on the continuum damage mechanics theory. The principal strain and the equivalent strain were used to judge the damage and failure state in the element, and the fracture simulation was performed. Then, the simulation results were compared with the corresponding experimental data to determine the prediction accuracy by using two kinds of strains. Results The fracture time in the simulation using the equivalent strain was remarkably later than that using the principal strain. Compared with the equivalent strain, the simulation results obtained by applying the principal strain were closer to the animal experimental results. Conclusions Under compression loads, it is more accurate to use the principal strain to determine the mechanical state of cortical bone element for fracture simulation. Through comparative method, a feasible numerical simulation method can be found to accurately simulate the fracture of cortical bone under compression loads, which can provide theoretical basis for improving the fracture prediction accuracy in clinic.