The invention discloses a door lock for a high-speed train of motor train units, which comprises a lock box. The lock box comprises a left lock shell and a right lock shell; a first lock bolt and a right lock cylinder are positioned at the right lock shell; the end of the first lock bolt is provided with a locating block; the right lock cylinder is provided with a toggle locating block and a movable toggle block for the first lock bolt; one side of the first lock bolt is provided with a sliding bar that can slide relatively to the right lock shell; the position on the right lock cylinder corresponding to the sliding bar is provided with a stop plate that can push the sliding bar to slide; one end of the sliding bar is connected with a gear assembly positioned on the right lock shell; one gear of the gear assembly is provided with a rotating shaft; the left lock shell is provided with a left lock cylinder which is coaxial with gears on the rotating shaft and the other end of the left lock cylinder is hinged with a second lock bolt and a connecting plate; the other end of the connecting plate is hinged with a third lock bolt arranged on the left lock shell. The door lock of the invention can be automatically locked or opened with the speed change of the high-speed train, thus improving the safety performance of the high-speed train.