Abstract: Once leakage happens to the wellhead of underground salt cavern gas storage, it may lead to fire or explosion, soit is of great significance to study on fire risk due to wellhead rupture at underground salt cavern gas storage. Spraying firedamage model is employed to analyze the fire risk, and quasi-transient model of the leakage gas rate and lost gas volumeunder the condition of wellhead rupture are established, and the prediction results can reflect the actual situation of theleakage due to wellhead rupture. At the same time, based on the thermal fluxes damage principle, the calculation formulaof damage radius is worked out and the relation between damage radius and salt cavern pressure is analyzed, which showsthat the damage radius becomes larger as salt cavern pressure goes higher. Therefore, it is pointed out that essential safetydistance shall be kept in the safety design of gas storage, and corresponding preventive measures shall be set up. The studycan provide important parameters and technical support to the result assessment of leakage of underground salt cavern gasstorage. Besides, it can provide theoretical guidance to the decrease of accident loss.