Abstract: The Double Cantilever Beam (DCB) test is the most primary method for determining the interlaminar fracture energy of composite laminate mode-I. In order to address the issue of inaccurate calculation of the mode-I fracture energy due to the resin-rich zone generated by prefabricated delamination from laying polytetrafluoroethylene film for DCB specimens, DCB tests with three laying angles (0//0,0//45,0//90) were designed and scanning electron microscopy was used to characterize the microstructure of DCB crack surfaces. the influence mechanism of resin-rich zone was quantified, and the nonlinear behavior of load-displacement curves under three working conditions of resin enrichment was studied. A numerical model of the DCB containing resin-rich zone and fiber bridging propagation zone was established to conduct quantitative analysis, interpretation, and reveal the mechanisms of the resin-rich zone on the fracture energy R curve. Experimental results show that the lengths of resin-rich zone corresponding to the three laying angles are significantly different, with the 0//0 specimen being the longest and the 0//90 specimen being the shortest. The coupling effect between the resin-rich zone and fiber bridging propagation zone results in different nonlinear behaviors in the load-displacement curves. The constructed numerical analysis model can accurately predict load-displacement curves consistent with experiments, verifying the influence of resin-rich zone on the initial fracture toughness of mode-I layer.