The application feasibility of hydroforming in frame longeron large parts is verified for the first time at home. The result of the research on the structure design and process analysis for frame longeron shows that hydroforming can be fully realized.With stiffness is comparison,collision test simulation and cross section force with traditional drawingassembly welding techniques,it has been found that hydroforming combining has multiple advantages such as lightweight, high stiffness,reduction in the number of parts,high precision,hence reduction the associated machining and welding and so on.It is especially suitable for forming various lightweight components used for the chassis parts in automotive.