To analyze quantitatively the interface of core-shell structural bamboo plastic composites (BPCs) surface, the relationship between the microstructure of composite surface and the macroscopic impact performance was investigated. The effect of shell layer on the interface and impact strength of the core-shell BPCs was studied by scanning electron microscope (SEM) images, computer image processing technique and fractal theory. The fractal dimensions of the core-shell BPCs were calculated and the relationship between the measured impact strength and the fractal dimensions of the core-shell BPCs fracture surface was discussed. The results showed that the fractal dimensions of the interface and fracture surface were within the range of about 2.1725 to 2.1970 and 2.2075 to 2.2204, respectively. All the correlative coefficients were higher than 0.99, therefore, the strong linear correlation indicated that the fractal characterization of the interface and impact fracture surface for the BPCs was possible, and also proved that the interface could be analyzed quantitatively depending on the feature parameters of the fractal dimension. The relationship between the fractal dimension and the measured impact strength was linear. The bigger the fractal dimension of surface, the bigger the impact strength and stronger the interfacial bond were. Thus, using the fractal dimensions the surface morphology of core-shell structural BPCs can be described and it may provide a new approach to investigate the inherent rules of fractal characteristics and Charpy impact strength of the BPCs with core-shell structure.