Abstract: The optimal setting of passageway railing is studied by the evacuation simulations in a subway station using a modified floor field model. In the modified floor field, the value of static field is redefined as the time instead of the distance to the exit. A control mechanism for the speed of evacuees is introduced in view of the specificity of the stair and escalator. Based on the analysis of evacuation efficiency, the main conclusions are as follows. First, passageway railing is not always an obstacle in the evacuation, but, on the contrary, it reduces the hidden danger and improves efficiency in a certain condition. Second, an optimal length of passageway railing is suggested to be 60% of the passageway in normal times while 100% in case of emergency or panic. Third, the lower running speed of escalator or the higher degree of conflict is, the longer the length of passageway railing is. Finally, the setting of passageway railing plays a part in balancing the capacity of stair and escalator mainly at low density, while alleviating the conflicts which result from exit reselection at high density