The invention relates to a grouting port sealing device for a concrete-filled steel tube support and effectively solves the problem that concrete is prone to leakage due to low strength of the grouting port and the problem about sealing of a grouting port. The grouting port sealing device is characterized in that the grouting port is formed in any steel tube of the circular-arc-shaped concrete-filled steel tube support, the steel tube located at the grouting port is sleeved with a circular-arc-shaped casing, and a hole having the same size and the same shape with the grouting port is formed in the circular-arc-shaped casing; before grouting, the circular-arc-shaped casing is moved along the steel tube, and the hole coincides with the grouting port; after grouting, the circular-arc-shaped casing is moved along the steel tube until the grouting port is covered with the circular-arc-shaped casing, circular-arc-shaped wedge bodies with end parts extending into the position where the circular-arc-shaped casing and the steel tube are connected are arranged at two ends of the circular-arc-shaped casing respectively, and the circular-arc-shaped casing and the steel tub are tightly combined by the aid of the circular-arc-shaped wedge bodies. The grouting port sealing device for the concrete-filled steel tube support is simple in structure, has better mechanical properties such as strength, rigidity, stability and the like, and can guarantee that the leakproofness of the concrete-filled steel tube support and the overall bearing capacity of the structure are not influenced by the grouting port.