In the background of the development of global low-carbon economy, to blossom the low-carbon transport is necessary for every country. Railway is recognized as a green transport with low-power consumption, less pollution, which is one of the most important infrastructures developed actively around the world. With the approaching era of high-speed railway, railway passenger demand has been paid much more attention. As passengers with different trip purposes are influenced by different factors when choosing means of transport, this paper will classify passengers by trip purposes and find the main influential factors according to different types of passengers with the aid of rough set. Then put forward initiatives aimed at improving passenger satisfaction, and enhance the positive attitude of passengers towards rail transportation.