The fatigue crack growth (FCG) model refers to the relationship between crack growth rate (defined as crack growth length versus number of cycles) and maximum tearing energy, and is used to predict the fatigue life of a rubber damping component. Usually, some of the measured relationships of crack growth length and number of cycles in a fatigue crack growth experiment cannot be used to model FCG, due to the stress softening phenomenon of filled natural rubber materials. In this study, a data processing technique is first given to obtain effective data of crack growth length versus number of cycles. Second, based on the assumption that maximum strain energy density and maximum strain have the function of the power relationship under a uniaxial tensile load, the model for modeling relations of crack growth length and number of cycles under variable amplitude loading conditions is established. Third, by using the least-squares method, the optimization method for identifying model parameters is established. On the basis of the established relations of crack growth length and number of cycles, the model for describing relationships between crack growth rate and maximum tearing energy is built, and the numerical method to obtain the constants in the mode is given. Finally, the proposed established crack growth model is validated by comparing the measured and calculated fatigue life of rubber dumbbell specimens.