The invention discloses an online drying device for a release film. The online drying device comprises a drying box body, guide rollers, fans, air outlet pipes, a film inlet, a film outlet and an exhaust fan. The film inlet is formed in one side of the drying box body, and the film outlet is formed in the other side of the drying box body. The multiple guide rollers which are arranged in parallel in an up-and-down manner are arranged in the drying box body in the direction from the film inlet to the film outlet. The two ends of each guide roller are connected with the inner side wall of the drying box body through supporting rods. At least one set of fans are arranged on each of the upper portion and the lower portion of the inner side wall of the drying box body. One row of air outlet pipes are arranged at the upper end of the drying box body. The exhaust fan is further arranged on the side, close to the film outlet, of the upper end of the drying box body. A set of universal wheels are arranged at the bottom of the drying box body. According to the online drying device for the release film, due to the fact that one set of fans are arranged on each of the upper portion and the lower portion of the interior of the drying box body, the effective drying area is enlarged, and the generation rate of defective goods is reduced; due to the fact that the guide rollers are arranged in parallel in the up-and-down manner, the heating area of the film can be effectively enlarged; and due to the fact that one row of air outlet pipes and the exhaust fan are arranged, humid air in the drying box body can be discharged out of the drying box body, and the drying efficiency is improved.