A gas tube structure includes a flexible tube. The end of the flexible tube is connected with a fixed connector. A sleeve is fitted on the fixed connector. The fixed connector and the sleeve are connected to a movable connector. The fixed connector has a connection section extending from an outer end thereof. The connection section has an annular seal groove and an annular buckle groove thereon. The sleeve has a sleeve hole therein, a stop flange at one end thereof and an engaging groove formed on in inner wall thereof. One end of the movable connector has a receiving hole and a C-shaped groove formed on an outer wall of the receiving hole. The C-shaped groove is adapted to receive a C-shaped buckle. The present invention has a stable connection, is safe for use, can lower the cost and enhances assembly efficiency.