The invention discloses a forming method for an upper flat-square of a bottom fork shaft. The forming method comprises a heating device, a feeding part, a heating part and a conveying part are sequentially arranged on a support from top to bottom, and the feeding part comprises a rotary disc, a fixing shaft and a hopper. A plurality of sliding grooves for storing the bottom fork shaft are formed in the rotary disc and penetrate through the rotary disc in the radial direction of the rotary disc, a vertical through hole is formed in the fixing shaft and can communicate with the sliding grooves, and a stepping motor for driving the rotary disc to rotate is fixedly installed on the support. The heating part comprises a heating coil, the heating coil is located below the rotary disc, and the heating coil and the through hole are coaxially arranged. A dark box is arranged below the heating coil, a blind hole is formed in the dark box, and a photoelectric sensor is arranged at the bottom of the blind hole. The photoelectric sensor is in electric connection with the stepping motor. The conveying part comprises a conveyor belt, a plurality of vertical pipes are arranged on the conveyor belt, and check blocks are arranged in the middles of the vertical pipes and are slidably connected with the vertical pipes in the transverse direction. Heat expansion blocks are arranged between the vertical pipes and the ends, away from the vertical pipes, of the check blocks, and labor burden of workers is relieved.