A new requirement for defect detection has been proposed for the application of the new methods such as friction stir welding and laser welding. Furthermore, it is also necessary to realize long time storage and automatic processing after manufacture and servicing in the digital workshop. At present, the detection of X-ray detection method has many shortcomings, for example the film can not be preserved in long time, the evaluation is depend on the level of operators and the testing automatic level is not enough. In order to make the testing of internal defects in the rail vehicle welding structure, more visible and automatized a digitalized X-ray testing and evaluating method is proposed. In this paper, a new digitalized device of X-ray film is constructed and the film can be scanned into the computer at low information loss. Then the finding,measurement and recognition of welding imperfection, evaluation of film is realized. At last, a testing database is established also to record and look back the weld film information.