Abstract: HT-350RTM, a novel high temperature polyimide resin for resin transfer molding (RTM) process, was synthesized through an optimized proportion of diamine monomer. 4-phenylethynylphthalic anhydride (4-PEPA) was employed as the end-capping agent of HT-350RTM resin, and 2, 3, 3', 4'-biphenyltetracarboxylic dianhydride (α-BPDA) used as its dianhydride monomer. U3160/HT-350RTM laminates were fabricated by RTM process reinforced by U3160 carbon fabric for evaluation of mechanical properties. The results show that the lowest melt viscosity of HT-350RTM is 390 mPa·s, and it stays below 1 Pa·s for over 2 h at 280℃, which qualifies the possibility for RTM process. After being cured, the glass transition temperature is 392℃ and the decomposition temperature(5% loss) is 537℃. The porosity of U3160/HT-350RTM laminates is only 0.34%. The U3160/HT-350RTM composites exhibit excellent mechanical properties at room temperature, and the retention rates of mechanical properties at 315℃ and 350℃ are both more than 60%, making the U3160/HT-350RTM composites ideal for the long-term use under 350℃.