A structure for fixing a foot ring to a supporting post of a chair, the structure comprising: a ring body, a hub arranged concentrically with the ring body, and a plurality of spokes radially arranged between an inner periphery of the ring body and an outer periphery of the hub, wherein the hub has a central hole formed with internal threads on an inner surface thereof; and a bush being a cylindrical body having a tapered outer surface with external threads formed thereon, wherein the bush has a shaft hole penetrating along a longitudinal axis of the bush, characterised in that two recesses are formed on the opposite sides of the inner surface of the shaft hole, the two recesses extend axially along the inner surface of the shaft hole from a first end of the shaft hole to a second end of the shaft hole, and two pads are respectively disposed on, fixed in and protrude from the recesses, the two pads are softer and have a higher coefficient of friction compared to a coefficient of friction of the inner surface of the shaft hole, and a groove penetrating through a wall of the bush, wherein two opposite sidewalls of the groove have a width spaced apart from each other, and form an angle (θ) in a widthwise direction thereof, wherein the range of the angle (θ) is 5° to 8°, wherein the range of the width is 5 to 10 mm, and wherein the bush is assembled with the hub by screwing the external threads of the bush with the internal threads of the hub, the supporting post is configured to penetrate through the shaft hole of the bush, and when the bush rotates toward a first direction, the wall of the bush is restricted by the central hole and the inner diameter of the shaft hole is reduced, configured to clamp and fix the supporting post, when the bush rotates toward a second direction, the wall of the bush restricted by the central hole is released to make the shaft hole enlarge to release the clamping and configured for fixing of the supporting post, wherein the first direction and the second direction are opposite to each other. a ring body, a hub arranged concentrically with the ring body, and a plurality of spokes radially arranged between an inner periphery of the ring body and an outer periphery of the hub, wherein the hub has a central hole formed with internal threads on an inner surface thereof; and a bush being a cylindrical body having a tapered outer surface with external threads formed thereon, wherein the bush has a shaft hole penetrating along a longitudinal axis of the bush, characterised in that two recesses are formed on the opposite sides of the inner surface of the shaft hole, the two recesses extend axially along the inner surface of the shaft hole from a first end of the shaft hole to a second end of the shaft hole, and two pads are respectively disposed on, fixed in and protrude from the recesses, the two pads are softer and have a higher coefficient of friction compared to a coefficient of friction of the inner surface of the shaft hole, and a groove penetrating through a wall of the bush, wherein two opposite sidewalls of the groove have a width spaced apart from each other, and form an angle (θ) in a widthwise direction thereof, wherein the range of the angle (θ) is 5° to 8°, wherein the range of the width is 5 to 10 mm, and wherein the bush is assembled with the hub by screwing the external threads of the bush with the internal threads of the hub, the supporting post is configured to penetrate through the shaft hole of the bush, and when the bush rotates toward a first direction, the wall of the bush is restricted by the central hole and the inner diameter of the shaft hole is reduced, configured to clamp and fix the supporting post, when the bush rotates toward a second direction, the wall of the bush restricted by the central hole is released to make the shaft hole enlarge to release the clamping and configured for fixing of the supporting post, wherein the first direction and the second direction are opposite to each other.