After opening of new-constructed DPL,the passenger trains on existing lines are reduced,which could increase the carrying capacity of freight trains on the existing lines and release freight transport pressure.Through analyzing the calculation method of carrying capacity of traditional freight cars,combined with actual situation of passenger train withdrawal on existing line,the influence of change of passenger train reduction coefficient and structure of different withdrawal passenger trains on carrying capacity is considered in this paper.Through determining the number of tracing passenger trains dispatching in succession and its deducted time,as well as calculating the number of scattered passenger trains,the calculation method of increasing carrying capacity of freight cars is put forward in the paper,and the calculation method is proved by example analysis on Shijiazhuang-Zhengzhou down direction of Beijing-Guangzhou line.