The basalt fiber was surface modified by high energy laser beam, and basalt fiber/epoxy resin composite was prepared. The microstructure, mechanical properties and phase structure of basalt fiber were characterized by scanning electron microscope, atomic force microscope and X-ray diffraction. The influence of laser on the microstructure and properties of basalt fiber was systematically studied. And mechanical properties of basalt fiber/epoxy resin composites were tested. The results show that the depth and area of surface defects of basalt fiber increase with the increase of laser modification power. When the modification power increases from 0 W to 120 W, the maximum depth of surface defects increases from 9 nm to 180 nm, the distribution range of surface defects increases from 3.5~6.5 nm to 90~120 nm, the surface roughness increases from 141 nm to 2470 nm. After laser modification, the tensile property of basalt fiber decreases. The relationship between the depth of surface defect and tensile strength of basalt fiber does not follow the classical theory because of the radiation effect of laser on the fiber. XRD peaks of basalt fibers are basically the same before and after laser modification, and the types of elements on the surface of basalt fiber do not change. Laser modification can improve the mechanical properties of basalt fiber/epoxy resin composite. With the increase of laser power, the tensile strength and impact of composites increase first and then decrease.