In order to explore the reliability of continuous shutoff of the shut-off valve in the continuous fire scenario after the UHV transformer oil conservator is installed with the shut-off valve, and the overall safety of the UHV transformer oil conservator under the condition of reliable shutoff of the shut-off valve in the continuous fire scenario, a fire safety verification test for the installation of a shut-off valve in the oil conservator of the UHV transformer was carried out. The test results showed that the shut-off valve didn’t fail after 18.5 minutes of continuous combustion under the full liquid fire scene of the UHV transformer, which verified the continuous shut-off reliability of the shut-off valve in the continuous fire scenario. The oil conservator used in this verification test was an external oil type capsule oil conservator. Under normal temperature conditions, the oil conservator was equipped with a shut-off valve. After burning continuously for 18.5 minutes in the full liquid fire scenario, the oil temperature in the oil conservator had not yet reached the state of high-temperature hot oil, and no violent fire such as explosion had occurred, which verified the overall safety of the UHV transformer oil conservator in the case of reliable shutoff of the shut-off valve in the continuous fire scene.