Abstract: To reduce the deformation defects of rail transit aluminum alloy car-body structure and car-body parts during processing， the deformation mechanism and causes are analyzed. At the same time， 4 solutions for different deformations including automatic edge finding method，tooling guarantee method，trial cutting method and machining allowance method are proposed，which are compared and analyzed based on the actual processing of the underframe beam and the side wall window frame. The results show that the proposed 4 solutions are suitable for different vehicle structures and parts processing respectively.