Fatigue fracture is a common failure type of engineering structures under load cycles. The crack existed in the structure is often a mixed-mode crack because the direction of the resultant load is not perpendicular to the crack surface. The mixed-mode crack does not grow along the direction of the initial crack surface, and it is different from that of mode I crack. Accurately predicting the behavior of crack propagation is of significance for crack growth rate evaluation. A common method is to simplify the broken crack as a straight line crack, which, however, will bring an accumulated error into the prediction of crack propagation while using the existing crack propagation criterion. The path calculated using that method deflects downwards, deviating from the real situation. In the present study, the cleavage angle is revised on the basis of analyzing the error caused by the common method, and the actual crack is simplified as an equivalent linear crack. Then, an equivalent modified model is proposed for describing the fatigue growth path of mixed-mode crack. The crack propagation of the mixed-mode crack can be predicted by incorporating this model into ABAQUS XFEM module. The proposed model is validated by the fatigue crack propagation experiments of 2024 aluminum alloy plate with inclined crack. It is found that the results predicted by the model are in agreement with the experimental results. First, the number of fatigue loading cycles computed using the proposed model is lower than that tested by experiments if the specimens are of the same initial crack length. The prediction using the present method is conservative. Second, the accuracy of the prediction is good if the cracked structure is mainly subjected to mode I load, while the maximum computed error is less than 10% if mode Ⅱ load is more significant.