By macro and micro morphology observations, chemical analysis, metallurgical observations, SEM observations and EDS analysis, the failure cause of a colored steel plate used as the workshop roof in a plant was analyzed; then, some improved measures were also proposed in this paper. It is demonstrated that failure of the colored plate is caused by the synergism of high temperature, and sulfur dioxide corrosion. The high concentration sulfur dioxide of the local area on the colored plate is the main failure cause.