Abstract: The present application discloses a glass fiber sizing composition. The glass fiber sizing composition comprises effective components and water, and has a solid content of 4.0% to 6.0%; and the effective components comprise a silane coupling agent, a film former, a lubricant, a surfactant, a leveling agent, an interfacial reinforcing agent, a wetting agent, a defoaming agent, and a pH regulator. A glass fiber produced by the sizing composition has desirable strand integrity properties, softness and high dispersibility after a certain tension; the glass fiber also has high permeation velocity and complete permeation effect in the epoxy resin. The glass fiber shows excellent interfacial compatibility with the resin, and is suitable for weaving technology, especially for producing a heavy wind blade fabric. A composite formed by vacuum infusion of the fabric and the epoxy resin has desirable static mechanics and fatigue properties.