The invention discloses a forming method for a sandglass-shaped metal structure. The forming method is characterized by comprising the following steps: preparing a plurality of elements; stacking theplurality of elements together to form a shape having a cross section area which is gradually increased from the middle to the two ends; welding and packaging the plurality of elements which are stacked together into a preform; and welding interferences among the plurality of elements together through forge welding to prepare a blank from the preform. According to the forming method disclosed by the invention, a plurality of metal blanks with smaller sizes are used as structure elements for preparing a large metal blank.