By controlling deposition time (5 h, 15 h, 30 h and 50 h), PyC interface with different thickness were obtained, and then S5, S15, S30 and S50-C/ZrC-SiC composites were prepared by precursor impregnation pyrolysis process. The effects of PyC interface thickness on the flexural and fracture properties of C/ZrC-SiC composites and its mechanism were studied. The results show that with the increasing of deposition time, the PyC interface thickness become bigger, and the flexural mechanical properties and fracture toughness of C/ZrC-SiC composites increase firstly and then decrease. This is mainly due to the release of fiber damage and fiber/matrix thermal mismatch with the increasing of PyC interface thickness, which will improve the strength of C/ZrC-SiC composites at last. But as PyC interface thickness become too larger, the bonding force between fiber and matrix and the content of ZrC SiC matrix will be reduced, which will eventually lead to the decrease of strength of C/ZrC-SiC composites. At the meantime, S30-C/ZrC-SiC composites exhibits more “fiber bridging”, “crack deflection” and “crack branching”, which are beneficial to the consumption of fracture energy, and therefore it shows better fracture properties.