Abstract: A beam model supported on two-parameter elastic subgrade and concerning the effect of the crack tip deformation is developed to analyze the four-point bending end-notched flexure (4ENF) specimen for mode II fracture. Based on the model, a linear relationship between average compliance and crack length is obtained for the 4ENF specimen. The accuracy of this model and the linearity of the average compliance–crack length relationship are verified by finite element analysis through wood–FRP bonded interface specimen. Close correlations of average compliance and compliance rate change between the model and finite element analysis are achieved, indicating that the present model is accurate in predicting the compliance and its rate change. The results coming from both the method using the global model and corresponding finite element analysis show that the average compliance rate change of 4ENF beam is independent on crack length, and that the calculation of the critical strain energy release rate does not require measurement of crack length propagation. Thus the necessity of extensive experimental compliance test can be alleviated and the need for crack length measurement is eliminated.