A brace has a shell formed within a contour that according to a person's ankle and a binding to fasten the shell onto the ankle. When the person is wearing an ankle support, the brace is mounted on an external surface of the ankle support and fastened by the binding. Such that the brace supports the ankle support and provides an extra constriction to the person's ankle to provide an extra effect of ankle immovability and impact cushion. The brace supports the ankle support via an inner surface evenly abuts the whole external surface of the ankle support. Thus, a pressure is evenly applied to the person's ankle and ordinary blood flow in the person's ankle portion is allowed so that the brace is comfortable to wear.