In order to detect the debonding defect in train door,the temperature distribution and variation on cover plate surface was obtained with the infrared thermal imaging.The factors affecting infrared thermograph quality of train door debonding defect were analyzed.The infrared thermograph detection for train door debonding defect was carried out indoor under a condition of heating,non static,non contact and penetrating way.The infrared thermograph video with a length of 180 s was gotten in the experiment.The ratio of the average temperature in debonding region to the average temperature in non-defect region is set up as a criterion.The characteristic could be used to detect debonding defect between cover plate and aluminum honeycomb of the train door.