Abstract: To improve the interfacial properties of basalt fiber/epoxy composites, the graphene oxide modified with coupling agent was introduced into sizing agent, and the modified sizing agent was used to modify basalt fiber and the graphene oxide-basalt fiber/epoxy composites were prepared. The modification effect of graphene oxide was characterized by FTIR. The effect of modified sizing modification on surface of basalt fiber and composites cross-sectional morphologies and reaction mechanism were investigated using SEM. The results show that coupling agent is successfully grafted onto the surface of graphene oxide. Surface roughness and reactive functional groups are increased after basalt fiber being infiltrated in sizing agent modified by graphene oxide, and the mechanical interlocking and chemical bonding of the graphene oxide-basalt fiber/epoxy interface are enhanced, the interface bonding strength is improved, the fracture strength of basalt fibers is improved by 30.8% and the interlaminar shear strength of graphene oxide-basalt fiber/epoxy composites is improved by 10.6%.