The emergency shut-off valve of oil tank truck, also known as submarine valve, is a kind of safety valve installed at the loading and unloading port of metal atmospheric tank body of liquid dangerous goods tank truck. Submarine valve structure: there is a spring installed on the top of the valve. When opening, it needs to rely on the lower stem rotation force to overcome the spring pressure to open the valve; when closing, it needs to seal the valve under the spring force. The rotation of the valve stem can depend on the handle or cylinder, so it is divided into manual subsea valve and pneumatic subsea valve. There is a flange on the top and bottom of the valve, which is connected with the oil tank on the top and the pipeline on the bottom.