Abstract: Proposed here is a mechanism scheme of the platform screen doors （PSD） for subways．In this scheme‚the mechanism structure is composed of four modular units and is equipped with a3D adjustable bottom supporter and  flexible top supporter．The constitution and function of the main mechanical parts are expounded．The external loads on PSD are investigated and the working condition as well as the verification criterions are presented．The mechanics model is simplified by the presumption that all parts consist of panel units and beam units．This scheme can satisfy the special requirements of subway stations on PSD‚and the dynamic model reflects the actual working conditions of PSD．

Key words:  platform screen door, mechanism design, mechanical model, subway station