Continuous silicon carbide fiber reinforced silicon carbide matrix (SiC f/SiC) composites are attractive candidate materials for aerospace engine system and nuclear reactor system. In this paper, SiC f/SiC composites were fabricated by polymer infiltration and pyrolysis (PIP) process using KD-S fiber as the reinforcement and the LPVCS as the precursor, while the BN interface layer was introduced by chemical vapor deposition (CVD) process using borazine as the single precursor. The effect of the BN interface layer on the structure and properties of the SiC f/SiC composites was comprehensively investigated. The results showed that the BN interface layer significantly improved the mechanical properties of the KD-S SiC f/SiC composites. The flexure strength and fracture toughness of the KD-S SiC f/SiC composites were evidently improved from 314±44.8 to 818±39.6 MPa and 8.6± 0.5 to 23.0±2.2 MPa·m 1/2, respectively. The observation of TEM analysis displayed a turbostratic structure of the CVD-BN interface layer that facilitated the improvement of the fracture toughness of the SiC f/SiC composites. The thermal conductivity of KD-S SiC f/SiC composites with BN interface layer was lower than that of KD-S SiC f/SiC composites without BN interface layer, which could be attributed to the relative low thermal conductivity of BN interface layer with low crystallinity.