The teeth of the bit break rock continuously when drilling in oil or gas well. However, the primitive crushing work ratio is used to evaluate single rock crushing effect, thus it is unsuitable to estimate and predict the second rock crushing and continuous breaking effects. Based on a second development of damage constitutive model in ANSYS software, the new models of crushing work ratio are developed. The applicability of the developed damage constitutive model and numerical simulation is verified by experiments and theoretical calculation under the condition of single rock crushing. Then the model is employed to analyze the single, the second and the total crushing work ratios. It is found that the evaluation model is efficient to predict the rock breaking effects of the second and total breaking by using the new crushing work ratio which decreases slowly with the increase of load. Moreover, the work ratios of the second crushing and the total crushing is reduced to approximately 80% and 60%, respectively, in comparison with the first crushing work ratio.