Abstract: According to the vacuum assisted resin infusion (VARI) technology, the formation mechanism and elimination method of the penetration and defects in the wind turbine blades of glass fiber/epoxy resin composites prepared by VARI method were studied. The results show that when the environment temperature is 25℃, the initial mixing time is 100 min, and the viscosity of mixed resin is 250 mPas, the exothermic temperature and permeability of the resin are the best. The use of flow guiding medium can decrease the difficulty of penetration and shorten the molding time. Through using triaxial glass fiber stitched fabric as 6 layers and inserting a continuous felt as the flow guiding medium, the best flow guiding effect can be obtained, and the penetration effect will be consistent, which can effectively reduce the influence of edge effect on the penetration. The penetration and defects can be reduced by increasing the feed port position of resin in L7000 (from the blade root to the feed port at 17 cm) and L19000(from the blade root to the feed port at 19 cm), and adjusting the mold temperature to 28℃.