The invention relates to the field of pipe machining, particularly discloses a hole expanding method based on pipe expanding equipment, and mainly solves the technical problems that in the prior art,transmission procedures between various machining stations and stations of workpieces are completed manually, the labor intensity is large, the efficiency is low and the concentricity tolerance of different pipe diameters is too large and pipe fitting is not tight due to the fact that machining and positioning are not accurate. The pipe expanding equipment comprises a welding frame and a triple mechanical arm assembly, wherein the triple mechanical arm assembly is arranged above the welding frame; the triple mechanical arm assembly comprises a movable frame, a gripper I, an expanding mechanism, a chain transmission roller line and a gripper II, wherein the movable frame is arranged on the welding frame, the gripper I is fixed on a gripper connecting plate, the expanding mechanism is arranged below the welding frame, the chain transmission roller line is arranged on the right side of the welding frame, and the gripper II is fixed on the gripper connecting plate. According to the method,the equipment automation degree is increased, manual operation is reduced, the equipment machining efficiency is improved, the accuracy of hole expanding machining of the equipment to the workpiecesis integrally improved, and accurate operation is realized.