The chopped fiber reinforced thermosetting polyimide composites (C–T700/HT–350RTM) were produced through molding process, and the chopped T700 carbon fiber (C–T700) were chosen as reinforcing material, the HT–350RTM polyimide were chosen as resin matrix. The influences of changing carbon fiber volume fraction on the coefficient of linear expansion and mechanical properties of C–T700/HT–350RTM composites were investigated. The experimental results showed that the coefficient of linear expansion of C–T700/HT–350RTM composites decreased with the chopped fiber volume fraction increased, and the tensile modulus, compression modulus, flexural modulus increased with increasing chopped fiber volume fraction, while the tensile strength and flexural strength first increased and then decreased, the compressive strength has slowly increased with the increasing of chopped fiber volume fraction.