Turn-back ability of the intermediate station is a key factor to determine the carrying capacity of the rail line in the multi-routing mode of urban rail transit. In this paper, we analyze the calculation principle of the turn-back ability of the intermediate station, and the calculation model of the minimum turn-back interval time is established. Taking 2.5 minutes as the train headway time, analyze the limiting factors of the intermediate turn-back station under the condition of the ratio of the short routing train and long routing train is 1:1, and use the simulation method to measure the relevant influencing factors. Studies have shown that the line-front turning-back stations with single cross line has restrictions on the capacity of the rail line, while the line-behind station reentry has no limit. When the interval is less than 2.5 minutes, the line-behind station with double turn-back line can be used to meet the turn-back ability requirement. In addition, the speed of arrival the station, the length of train, the position of enter the station and the train dwelling time at station have a certain impact on the turn-back ability. The train dwelling time at station and the speed of arrival the station has a great influence on the turn-back ability. When speed arriving at the station is less than 60 km/h, the increase of speed improves turn-back ability obviously.