Automatic support structure for seat mattress of motor vehicle

The utility model discloses an automatic supporting structure for a seat cushion of a locomotive, which mainly comprises a first and a second supporting arms, at least a spiral spring, a damping device, etc., wherein the damping device is arranged in each spiral spring in a cylinder shape, and the first and the second supporting arms are respectively combined with both ends of the damping device so as to form the pivot. Both end parts of each spiral spring respectively support the first and the second supporting arms, and the first and the second supporting arms are additionally and respectively combined with a seat cushion and a locomotive body of a locomotive. The first and the second supporting arms can retain the force of staying and expanding by using the elastic force of each spiral spring, and the seat cushion can be directly rotated upwards to open after the clamping is unlocked. The damping device can limit the rotating speed of the first and the second supporting arms so as to decelerate the upper and lower speed of the seat cushion, and can avoid the injury caused by that the seat cushion quickly bounces up or falls down for the user.