Poly(silylene arylacetylene) (PSA) resin is a new kind of polymer materials with excellent heat resistance, usually used as resin matrices for composite materials in aerospace fields. However, the interfacial adhesion between fibers and PSA resin is weak. In this work, the interface properties of T300 carbon fiber reinforced PSA resin composite were studied. Firstly, T300 carbon fiber cloth was treated at various temperatures, characterized by TG, FT- IR, XPS and SEM, and then the T300/PSA composites were prepared. Secondly, a benzoxazine with terminal acetylene (BA) was used as a coupling agent and coated on the surface of T300 cloth which was treated at high temperature, and then the T300/PSA composite with BA was prepared. The results show that high temperature treatment can improve the mechanical properties of the T300/PSA composites. What’ s more, the coating of BA coupling agent can further improve the mechanical properties of the T300/PSA composites. The flexural strength of T300/PSA composite at room temperature is increased up to 413.1 MPa, with an increase rate of 53.9% ; and the flexural strength at 450 ℃ is increased up to 295.5 MPa, with an increase rate of 44.3%.