It reviews the main methods of the study of railway capacity in the world. But in China, the defini-tion of railway capacity is different from the other countries, so the main methods of calculating railway ca-pacity are not suit to Chinese railway. We introduce the coefficient of removal analysis method to calculatethe capacity of railway with automatic block section, but its calculating result isn’t satisfying. As computertechnology improves, the auto-drawing train working diagram (TWD) has become a trend. It proposes a newapproach to calculate the railway capacity, and the calculating method is based on auto-drawing TWD andcomputer simulation. The goal of this new method is to draw the maximum number of common freight trainpaths into the original timetable where passenger train paths and important freight train paths are exist andfixed.