Abnormal locomotive roof equipment status and foreign matter are one of the factors that affect the normal operation of locomotives. Research and application of locomotive roof status and foreign matter detection technology is of great significance to the safety of railway. This paper first discusses the three detection technologies in the status detection of locomotive roof equipment, which are mechanical contact type, non-contact type based on linear images, and comprehensive dynamic monitoring type. The application scenarios suitable for these technologies and the advantages and disadvantages are explained and compared; On the basis of traditional manual foreign matter detection, this paper focuses on the roof foreign matter detection technology based on image processing, summarizes the technical methods used in the locomotive roof imaging, image preprocessing, and foreign matter detection, and points out the development trend of the locomotive roof foreign matter detection technology and the main content to be studied.