Abstract: For rail transit lines that adopt CBTC system, the bottleneck point that restricts the operation capacity of the line is usually the turn-back capacity of the station-back return station, and the influence of the turnout speed limit on the capacity of station-back return station is particularly obvious. Based on an analysis of the turnout lateral speed limit and the turn-back capacity calculation, the influence of turnout lateral speed limit on the turn-back capacity is studied, suggestions to improve the turn-back capacity are put forward.