C/C composites are a new type of high-performance composites,but their shortcomings of high brittleness and poor toughness limit their wide application. Therefore,in this study,three kinds of C/C composites were designed and prepared using the chemical vapor infiltration (CVI) method with matrix carbon: rough layer,smooth layer,and rough layer/isotropic layer band-structured pyrolytic carbon(PyC),respectively. And the microstructures,fracture behaviors,and toughening mechanisms of C/C composites were investigated. The results indicate that the flexural strength of the three C/C composites is 189.1,191.5,and 233.5 MPa,respectively. The C/C composites with rough layer and band-structured carbon matrix are pseudoplastic fractures. In contrast,the C/C composites with smooth layer carbon matrix are brittle fractures. Compared to the C/C composites with rough layer carbon matrix,the C/C composites with band-structured carbon matrix show a significant increase in toughness through interfacial sliding between the different structured pyrolytic carbon,which increases strain amount by about 70%. Therefore,the toughness of C/C composites can be effectively optimized by controlling the parameters of the CVI process to achieve band-structured pyrolytic carbon preparation.