Abstract: Interfacial reaction will have a significant impact on the mechanical properties of titanium matrix composites. In order to determine the diffusion of elements and the growth law of interfacial reaction layer of SiC_f/TC18 composites, SiC_f/TC18 composites were prepared using magnetron sputtering precursor wire method and hot isostatic pressing process. Heat exposure experiments were conducted at different temperatures (400, 600, 800℃) and time (50, 100, 150, 200 h) to analyze the changes in interfacial reaction layer thickness, element distribution, and diffusion patterns of SiC_f/TC18 composites in hot isostatic pressing and hot exposure states. More importantly, this work elucidated the mechanism of element mutual diffusion, summarized the growth law of interface reaction layer thickness with heat exposure time, and revealed that the interface reaction layer products of SiC_f/TC18 composites are mainly TiC. After calculation, the interface index factor of SiC_f/TC18 composites was 4.0×10⁻⁶ m/s^1/2, the activation energy of reaction layer growth was 80.31 kJ/mol, the material exhibited excellent interfacial thermal stability at below 400℃.