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Abstract: The thin-walled cylindrical parts with ribs, as the main structure of the launch vehicle, has been currently used in block manufacturing mode, which has the disadvantages of long manufacturing cycle, low material utilization rate and limited structural lightweight. Therefore, the integral forming process of the thin-walled cylindrical parts with ribs is an inevitable development trend. At the same time, studies have shown that the application of composite energy fields in the plastic forming process can help reduce the forming load and promote material flow. In this paper, a new method of ultrasonic-assisted spinning-extrusion integral forming for thin-walled cylindrical parts with outer ribs was proposed, which could not only improve the manufacturing efficiency of ribbed cylindrical parts, but also further improve the forming height and uniformity of outer ribs. A simulation model of ultrasonic-assisted spinning-extrusion for thin-walled cylindrical parts with vertical and horizontal outer ribs was established, the influence of ultrasonic amplitude on the forming accuracy of vertical and horizontal outer ribs was obtained, and the mechanism of ultrasonic vibration improving the forming accuracy of vertical and horizontal outer ribs was revealed. On this basis, ultrasonic-assisted spinning-extrusion equipment was built to verify the feasibility of this process. The results showed that with the increase of ultrasonic amplitude, the forming height of vertical and horizontal outer ribs gradually increases, and the effect of raising the forming height of longitudinal ribs is higher than that of transverse ribs. In addition, the introduction of ultrasound improves the filling of materials. As the ultrasonic amplitude increases, the uniformity of the forming morphology of the outer rib is also improved. The spinning-extrusion of the outer rib is mainly realized by the material flow in the tangential and radial directions. The ultrasonic vibration improves the material flow properties in these two directions, and promotes the filling of the material into the rib groove, thereby increasing the spinning-extrusion forming accuracy of the outer rib. The forming height of the outer rib was measured with or without ultrasonic vibration. When the rolling reduction is 1 mm, the average forming height of the outer rib with ultrasonic amplitude of 9μm is nearly double that of the outer rib without ultrasound, which provides a new research idea for the integral forming of the spinning-extrusion of thin-walled cylindrical parts with vertical and horizontal ribs.