The invention relates to the technical field of X-ray transmission imaging security checking, in particular to a luggage castor detecting method in an X-ray security checking device, and provides a method for identifying luggage castors in an image of the X-ray security checking device. The image object identification technology is used for reference, and based on the characteristics of the castors in the aspects of specific materials, specific shapes, specific positions and the like, the identification method includes the steps that castor shafts are firstly found, and then the castors are judged. By means of the method, the positions and the ranges of the castors in the luggage image can be found, so that basic information is provided for luggage content analysis, fault alarms due to the fact that the castors are misjudged to be explosives are reduced, and the security checking efficiency is improved.