Narrow gauge refers to the track below the standard gauge1435 mm. The current standard in China is the standard gauge of 1435mm, while the current standard in Japan is mainly the narrow gauge of 1067mm. During the puppet Manchukuo period, the standard in Northeast China was1.067mm. However, because the standard of northeast railway construction is 1.524mm, the Japanese changed it to 1.435 standard gauge when revising. Therefore, during the period of the Puppet Manchukuo, the construction method of three-track parallel or four-track parallel was adopted in Northeast China. So there were narrow rails and standard rails.