According to the Railway Law (amended) in 2017, there are many railway transport companies on Vietnam Railway, each railway transport company owns a certain number of freight cars. To carry out the transportation, companies must work together to use the common wagon fund, giving rise to the exchange of wagons. Meanwhile, the choice of the wagon exchange plan is made manually and subjectively decided by the participants in the daily adjustment and granting conference without calculating economic efficiency, select the optimal plan for rail transport companies to rent wagons and wagon car rentals. Solutions have been put in place, but mainly for railway transport statistics, ie the top part of the exchange of freight cars. So in this paper, the author built a mathematical model, found a solution method and applied information technology to select the best plan for exchanging freight cars for railway transport companies.