Fault diagnosis technology plays a vital role in the traction transformer of electric locomotive, however, the traditional ant colony algorithm has certain limitations for the solution of fault diagnosis problems, and its effect is relatively unsatisfactory. Electric locomotives play an indispensable role in the arteries of modern rail transport. The failure of the traction transformer, which is the “heart” of the vehicle, can lead to the paralysis of the entire transportation system. Therefore, it is of great significance to study the efficient fault diagnosis technology of electric locomotive traction transformer to ensure the safe operation of the railway and improve the economic benefits. The purpose of this paper is to discuss the fault diagnosis technology of traction transformer of electric locomotive based on improved intelligent algorithm, and to emphasize its remarkable effect in practical application.