A carbon-fiber product forming device is disclosed. The device includes a first chamber forming with a hollow cavity, a hot-pressing plate disposed inside the hollow cavity, a mold disposed on the hot-pressing plate and formed with an outward opening, an air bag disposed inside a mold cavity of the mold, provided with a bag opening disposed near the outward opening, and attached on an outer surface thereof with carbon-fiber composites, a second chamber mounted on one side surface of the first chamber and disposed on wall surface with an air extracting port, an air inlet port, a heat medium entry port, and a barometric port, and a plurality of barometric pipes included inside the second chamber. Two ends of each of the barometric pipes are connected to the barometric port and the outward opening, respectively, such that the air bag could be periodically injected with air. A heat medium is injected into the inside of the hot-pressing plate when the air inside the hollow cavity is extracted by a vacuum pump via the air extracting port. The accordingly made carbon-fiber product has residual-air-removing rate of preferably above 99% and structural strength improvement of at least 5%.

Method for manufacturing a preform element used in particular for manufacturing a rotor blade of a wind turbine, wherein the preform element includes one or more components provided with at least one adhesive agent, wherein the components are arranged on a molding surface of a mold, wherein at least one bladder is arranged on top of the components and/or underneath the mold and wherein at least one fluid is supplied to the bladder for heating or cooling of the adhesive agent.