Low-temperature fixed ball valve

The invention provides a low-temperature fixed ball valve which mainly solves the problems that the pressure relief effect of a central valve cavity of an existing low-temperature fixed ball valve is bad so that the sealing effect of the valve may be influenced and the valve is prone to leakage. The low-temperature fixed ball valve is characterized in that a first valve seat support ring is provided with a pressure relief hole. The central valve cavity is communicated with a fluid passage in one side of a ball body through the pressure relief hole. The low-temperature fixed ball valve has the advantages that when the pressure in the central valve cavity rises abnormally, the pressure can be timely and fully released into the fluid passage, so that the pressure in the central valve cavity keeps the same as the pressure in the fluid passage; therefore, the low-temperature fixed ball valve is simple in structure, timely in pressure relief, good in pressure relief effect, good in sealing effect and free from leakage, and the sealing effect on the valve will not be influenced.