Pneumatic three-way ball valve is a kind of valve, which can be divided into L type and T type. The L-type three-way ball valve is used to switch the flow direction of the medium and can connect two mutually perpendicular channels. Three-way ball valves generally adopt a two-seat structure, and can also adopt a four-seat structure according to user requirements. The four-seat sealed three-way ball valve has beautiful appearance, compact and reasonable structure. It can not only realize the switching of the medium flow direction, but also make the three channels communicate with each other. At the same time, it can also close any channel to connect the other two channels for flexible control. Confluence or divergence of media in pipelines.