The invention discloses a molded pulp forming device with a double-side pulp sucking function and a using method thereof. The forming device comprises a rack, a pulp sucking lower mold, a hot-pressing lower mold, a hot-pressing upper mold, a top plate, a pulp feeding pipe, a pulp discharging pipe, a pulp sucking upper mold and a product forming mold, wherein the hot-pressing lower mold, the hot-pressing upper mold, the pulp sucking upper mold and the pulp sucking lower mold are provided with blowing pipes and vacuumizing pipes, and the pulp sucking surfaces of the pulp sucking upper mold and the pulp sucking lower mold are covered with pulp hanging net covers to which pulp can adhere. In use, the fives steps of pulp feeding, pulp sucking, pressing forming, mold closing and hot-pressing molding are conducted to obtain a product. The device is novel in concept and reasonable in design; upper and lower double-side pulp sucking is achieved by additionally arranging the pulp sucking upper mold, two independent pulp layers are formed, and the two pulp layers are combined into one after being subjected to pressing forming to form the integrated molded pulp product. Compared with the prior art, the compactness of the product is guranateed while the thickness of the molded pulp product is greatly increased, so that the molded pulp product is firmer and safer to use.