For forming of the cup-shaped piece for 2A12 material with a ladder-shape，the traditional forming process is a single process that step by step to accumulate into a multi-ladder through repeated heating, which will lead to low dimensional precision, high energy consumption, low efficiency, low heat resistance of die guide post and guide sleeve for using several sets of molds, multi-channel extrusion, repeated positioning error accumulation. For straight sidewall rib and step shape in the traditional extrusion, it is very difficult to form rounded corners less than R05mm. Through finite element simulation and process optimization, a new technology was gained to form ladder-shaped and small rounded corners by once heating, once placing workpiece using cross key die mouth oriented structure and method of continuous extrusion to control the order of the flow direction. With new technology the working hours are reduced, product performance and material utilization are improved, which provide a reference to form small rounded corner and multi-step products with short process transformation technology.