Forming method of thin-walled cylindrical part with large length-diameter ratio

The invention discloses a forming method of a thin-walled cylindrical part with a large length-diameter ratio. The machining process is blanking, spheroidizing annealing, blank machining before spinning, spinning forming, quenching and tempering treatment and flat end face finish-machining in sequence. According to the spinning forming, a core mold is sleeved with a spinning blank, the spinning blank is axially clamped to the core mold through a forward-spinning locating table on the inner wall of a front end opening, and forward-spinning pressing is conducted backwards from the front end of the spinning blank by adopting a spinning wheel, so that the wall thickness of the front half section of the spinning blank is matched with the wall thickness of a product until the rear end of the spinning blank is stretched backwards to the root of the rear end of the core mold; and then the spinning wheel is adopted to continue backward reverse-spinning pressing from the ending point of forward-spinning pressing until