Graphene fiber has attracted much attention due to its potential applications in supercapacitors, dye-sensitized solar cells, actuators, motors, stretchable circuits and functional composites, owing to its high electrical conductivity, tensile strength and good flexibility. The high tensile strength of graphene fiber renders it promising candidate as the reinforcement in the composites. The interface is the key element for the fiber-reinforced composites; however, there is no study about the interfacial evaluation about the graphene fiber reinforcement composites. Herein, in this study, we fabricate the high-strength graphene fibers (up to 890.1 MPa) through the wet spinning and thermal annealing method, make the graphene fiber-reinforced single-fiber composite, and develop a novel and facile fragmentation test to quantitatively evaluate the interfacial performance of graphene fiber. Graphene fiber has the interfacial shear stress (IFSS) of 60.6 MPa, exhibiting one of the highest IFSS among the carbon nanotube yarns and commercial carbon fibers composites. The superior interfacial performance of graphene fiber is attributed to the surface wrinkles and grooves, which establishes strong physical interlocking between graphene fiber and resin, favoring for the stress transfer. This work will pave the way for the development of graphene fiber-reinforced composites.