Stainless Steel Socket Welding and Threaded Union is composed of a spigot, a socket, a socket slot, etc. It is characterized in that there is a socket slot on the spigot, and the spigot and the socket are located at both ends respectively; compared with the prior art, it has a reasonable design, simple operation, strong practicality, and improved operation quality and convenience. The Union can be widely used in pipes of different diameters, and can also be used in water meters and valves. Due to the use of the spigot structure, the Union reduces the cost, is extremely convenient to install, use, and maintain, and has a very high leak-proof ability.