Abstract: In order to promote the stiffness and thermal dimensional stability of carbon fiber/epoxy composites, carbon fiber network reinforcement (CFNR) was fabricated firstly by short carbon fiber, and mixed with epoxy to prepare new type of CFRN/epoxy composites. Then, the microstructure and thermal mechanical properties of CFRN/epoxy composite were characterized by scanning electron microscopy and thermal mechanical analyzer, respectively. The results indicate that there are obvious network nodes of carbon-based adhesive points in CFNR/epoxy composites, and CFNR/epoxy composites exhibit relatively high electric conductivity, high stiffness and low thermal expansion, the elastic modulus is about 3 times and 6 times of that of regular short carbon fiber/epoxy composite and pure epoxy, respectively. The average thermal expansion coefficient (60-200 ℃) is 1/15 of that of regular short carbon fiber/epoxy composite, and 1/40 of that of pure epoxy, respectively. With the temperature increasing, the elastic moduli of CFNR/epoxy composite, regular short carbon fiber/epoxy composite and pure epoxy are dropping due to the softening of epoxy. When the temperature is above 80 ℃, the elastic modulus of CFNR/epoxy composite is about 7 times of that of regular short carbon fiber/epoxy composite, and nearly 70 times of that of pure epoxy. The research conclusions can provide experimental basis and theoretical direction for the exploring of polymer matrix composites with high stiffness and low thermal expansion.