The invention relates to a tube diameter expansion device. The tube diameter expansion device comprises a cylindrical seat, an elastic piece mounted in a stress groove and an expansion cone mounted in a bearing part, wherein the stress groove is formed in the first end of the cylindrical seat, and the bearing part is arranged at the second end; the elastic piece can receive thrust so as to drive the cylindrical seat to move. The elastic piece can absorb the instantaneously loaded thrust and then drives the cylindrical seat to move. In the initial phase for expanding a tube by using the tube diameter expansion device, the tube diameter expansion device moves gently instead of accelerating instantaneously, so that adjustment of the tube diameter expansion device and correction of the position of the tube diameter expansion device can be performed timely.