Blow molding method and system

The invention discloses a blow molding method and system. The blow molding method comprises the following steps that a prepared material is heated and melted; a mold is closed and heated to the preset temperature; a parison is extruded to the upper end of the mold, and downward negative pressure traction is supplied to the bottom of the mold at the same time, so that a cavity of the mold is rapidly filled with the parison; meanwhile, air is blown into the parison, so that the outer surface of the parison is attached to the inner surface of the cavity of the mold; and after the parison is subjected to pressure maintaining for a preset time, the mold is opened, and a finished product is taken out. According to the blow molding method provided by the invention, the process that mold closing is conducted at first, and then blanking is conducted is adopted; the parison is pulled through the negative pressure traction; after being subjected to blanking, the parison can rapidly and stably enter the cavity of the mol