Abstract: A plug for a liquid container comprises an outer plug, an inner plug and a fixing device. The outer plug is substantially a cylinder shape with a bottom wall and detachably installed onto a liquid container, wherein a liquid passage hole is penetrated through the bottom wall, and a liquid passage is formed between the bottom wall and an upper opening of the outer plug body. The inner plug is pivotally connected to the outer plug through a hinge, wherein the inner plug further comprises a liquid inlet seal member for sealing the liquid passage hole and a liquid outlet seal member for sealing an inner wall near the upper opening of the outer plug. The fixing device is used for fixing the inner plug onto the outer plug.