Abstract: Extreme environments in aerospace require composites to have both good thermal conductivity and excellent mechanical properties, however, the inherent low thermal conductivity of carbon fiber/epoxy (CF/EP) composites interlayer epoxy resins limit their application scope. In this paper, using the high thermal conductivity of mesophase pitch-based carbon fibers (MPCF) and the high strength of polyacrylonitrile-based carbon fibers (PAN-CF), the two kinds of carbon fibers were used to prepare MPCF/PAN-CF hybrid felt by wet netting process, which was then used as three-dimensional thermal conductivity pathways in the area of the epoxy resin between the layers of the composite material. Subsequently, CF/EP composites were prepared by vacuum-assisted resin infusion (VARI) process after alternating layers of hybrid felt and carbon fiber cloth. The effects of MPCF/PAN-CF hybrid felt with different areal densities on the thermal conductivity of CF/EP composites in different directions and on the mechanical properties of CF/EP composites, such as the interlaminar shear strength, interlaminar fracture toughness of mode II(G_IIC), and the flexural strength were investigated. The results demonstrate that the in-plane thermal conductivity of CF/EP composites gradually increases with the increase of the hybrid felt surface density, in which the in-plane thermal conductivity of the composites reaches 58.51 W/(m-K) after the incorporation of 15 g/m² MPCF/PAN-CF hybrid felt, which is an enhancement of 766.8% compared with that of the reference samples without incorporation of the hybrid felt. Meanwhile, the interlaminar shear strength, G_IIC values, and flexural strength, modulus of CF/EP composites is improved with the addition of the hybrid felt. The MPCF/PAN-CF hybrid felt forms a thermally conductive-mechanically enhanced dual network of MPCF/PAN-CF with ordered interconnections in the interlayer epoxy region of CF/EP composites, which accelerates the diffusion of heat within the CF/EP composites and effectively improves the mechanical properties of the composites at the same time.