The utility model discloses an axial end face fixing water seal of a finish rolling supporting roller. The device comprises a supporting roller, a bearing box and a bearing, a supporting roller shoulder ring is fixedly arranged on the outer end face of the supporting roller, a clamping ring used for limiting the axial position of the bearing is fixedly arranged on the inner side of the bearing box, a sealing cavity is formed between the supporting roller shoulder ring and the clamping ring in a matched mode, and a water seal structure is arranged in the sealing cavity. In the using process, the device is convenient to use; the inner fixed sealing ring is tightly sleeved on the back-up roll shoulder ring; a reliable sealing structure is formed between the inner fixed sealing ring and the supporting roller shoulder ring; the outer movable sealing ring movably sleeves the outer side of the inner fixed sealing ring in a sealing manner; the inner fixed sealing ring and the outer movable sealing ring are sealed reliably, the outer movable sealing ring abuts against the clamping ring, reliable sealing is formed between the outer movable sealing ring and the clamping ring, and the interiorof the bearing box is separated from the outside in a sealed mode through the three sealing structures.