The fully welded ball valve is a ball valve whose valve body is formed by one or more welding seams. It can be directly welded and connected to the pipeline, saving resources such as flanges, gaskets, bolts, etc. It has a small volume and light weight, is convenient to install, and easy to insulate. It has a bi-directional seal and low resistance when fully open. Moreover, it has the advantages of maintenance-free, bi-directional zero leakage, and low operation cost. It has increasingly become a substitute product for valves that require a large amount of maintenance work, such as butterfly valves and gate valves, and is widely used in branch network and heating stations.