Abstract: Low viscosity and high-temperature resistant isomeric polyimide resins were synthesized by modified polymerization of monomer reactants (MPMR) method. The effect of molecular mass on the rheology of oligmers and thermal-oxidation stability of cured resins was studied. The molecular structure of polyimide resins, the processing and mechanical properties of their composites were characterized. The results show that the shelf life of resin solution is more than two months. The lowest viscosity of PI-2 resin after imidization is 154 Pa·s. The temperature for 5% mass loss of cured resins is higher than 560 ℃. The flexural strength and flexural modulus of quartz fabric/PI-2 composite at room temperature and 500 ℃ are 917 MPa, 197 MPa and 29 GPa, 22 GPa, respectively. The tensile strength and tensile modulus at room temperature and 500 ℃ are 760 MPa, 341 MPa and 32 GPa, 31 GPa, respectively. The compressive strength at room temperature and 500 ℃ is 570 MPa, 95 MPa respectively. The interlaminar shear strength at room temperature and 500 ℃ is 62 MPa and 10 MPa, respectively.