Abstract: Driver-machine interface (DMI) unit is user interface of the train operation monitoring device (LKJ). Through the research of image character recognition method, this article designed a character recognition method based on "Dot Matrix Contrast" to recognize the characters in the DMI unit image. The result of identification was provided to the system verification program. By comparing the character lattice information in the interface with that in the font library, the character information displayed in the interface could be obtained. After a large number of image recognition tests, the recognition accuracy can reach 98%, and the recognition time for the whole image is less than 1 second. The results show that the character recognition method based on "Dot Matrix Contrast" can meet the requirements of the system verification program.