Abstract: The microstructure and tensile properties of the carbon nanotube fibers were studied, and then the interfacial shear strength and microstructure of the interface between carbon nanotube fibers and epoxy matrix were analyzed.The single fiber fragmentation test was used to test the interfacial shear strength of the carbon nanotube fiber/epoxy composites.Combined with the polarized light micrographs during single fiber fragmentation test, Raman spectroscope images of the composites and scanning electron microscope images of fracture surface, the interface microstructure of the carbon nanotube fiber/epoxy composites was studied.The results show that the interfacial shear strength of the carbon nanotube fiber/epoxy composites is about 14 MPa.During the formation of the interface between carbon nanotube fibers and epoxy matrix, epoxy can permeate into the carbon nanotube fibers and form a compound phase with a certain thickness, and this infiltration process and formation of the compound phase are beneficial to the bonding between the carbon nanotube fibers and matrix.