Abstract: The door sill includes a sill deck and a rail carrier assembly having a function of height adjustment. The rail carrier assembly is configured on the sill deck. The rail carrier assembly includes a rail cap, a rail carrier, an adjustment nut and an adjustment screw. The rail cap is snapped onto an upper end of the rail carrier. A groove is formed in the sill deck for the rail carrier to fit in. A nut installation hole is formed in the rail carrier. The adjustment nut is assembled at the nut installation hole, and is in threaded fit with the adjustment screw. The adjustment screw drives the adjustment nut to move up or down in an axial direction of the adjustment screw through rotation, thereby altering the height of the rail carrier fitted in the groove and altering the height of the rail cap.