In the R & D of the chrome frame of an automotive parts factory,the cracks formed at the lower corner around 120 ℃ after high temperature baking at 100 ℃ and climate change test. In this paper, X-ray thickness measurement method, microscope, internal stress analysis by glacial acetic acid and computer simulation were used to analyze the crack defects of the automobile interior chrome frame. Results indicated that the overlarge welding stress between outer panel and inner panel limited the expansion of inner panel and chrome frame under the high temperature situation. Consequently, the chrome frame was subjected to a greater expansion stress, resulting into the cracking of stress concentration area. After the optimizing of welding points between outer panel and inner panel,the welding stress decreased and the formed space was enough for the expansion of the the inner panel,and therefore,the problem was solved successfully and the quality requirement was met.