Abstract: Abstract: In order to study the rupture mechanism of the bamboo plastic composites (BPCs) with core-shell structure, in this paper bamboo residue fibers and high density polyethylene (HDPE) were used as materials of core layer; HDPE, bamboo pulp fibers/HDPE, nano-CaCO3/HDPE and white mud/HDPE, were respectively used as materials of shell layer to manufacture the BPCs with core-shell structure by coextrusion technology. The ratios of bamboo pulp fibers, nano-CaCO3 and white mud to HDPE in the shell layer structure were to be 10:90 respectively. To present the theoretical relationship between fractal dimensions (D) and the impact strength (?), and analyze the effects of different shell layer materials on the impact strength in the BPCs with core-shell structure, Charpy non-notched impact strength of the BPCs with core-shell structure was measured at room temperature according to ASTMD6110-2010. The fractographs of the BPCs with core-shell structure that had different shell layer materials were observed by scanning electron microscope (SEM). The impact fracture surface topography of BPCs manifested self-similarity. Based on fractal theory and computer image processing technology, a MATLAB program which computed the fracture's box-counting dimension of the BPCs with core-shell structure was designed. The digital image was transformed into factual image, and the charpy impact fracture surface fractal dimensions of the BPCs with core-shell structure that had different shell layer materials were measured by pixel-covering method, to investigate the relationship between impact strength and fractal dimension of the BPCs with core-shell structure. Results showed that the BPCs fracture possessed fractal characteristics and there were differences for the fractal dimensions of the BPCs with core-shell structure that had different shell layer materials. The fractal dimensions of the fracture surface were within the range of from 2.2075 to 2.2204, the linear degree of fitted beeline of MATLAB program was high and the correlation coefficients obtained were more than 0.98. The strong linear correlation indicated that impact fracture surface of the BPCs with core-shell structure had significant fractal characteristics. The impact fracture topography of HDPE in the shell layer was the most complicated in 4 kinds of fractures of the BPCs with core-shell structure, and the fractal dimension was up to 2.2204; the impact fracture topography of white mud/HDPE in the shell layer was more regular, and the fractal dimension was the smallest. The results accorded with the observed results by human eyes. The impact strength of the BPCs with core-shell structure containing HDPE shell layer material was the best and that containing white mud/HDPE had the worst performances. And the relationship between impact strength and fracture surface fractal dimension of the BPCs with core-shell structure obeyed exponential function roughly. Thus using the fractal dimensions to describe the impact fracture surface morphology of the BPCs with core-shell structure may provide a new approach to investigate the inherence rule between fractal characteristics and charpy impact strength of the BPCs with core-shell structure.