Abstract: The ultra-high temperature composite was fabricated based on polyimide containing biphenyl structure as the matrix resin and carbon fiber AS4. The rheology of polyimide precursor prepared by a modified polymerization of monomeric reactants approach (MPMR) was studied. The flexural strength and flexural modulus of the composite at RT and 371℃ are 1190 MPa,763 MPa and 121 GPa, 116 GPa, respectively. The shear strength of the composite at RT and 371℃ are 42 MPa and 26 MPa. The mechanical property of the composite can reach half of its mechanical property at room temperature. The glass transition temperature is up to 472℃ by DMA. The weight losses of the resin and composite at 371℃ for 100 h are 1.9 % and 2.0 %.