球阀的阀芯是球形体，由圆形通孔通过軸线，当球旋转90度时，在进、出口处呈现球面，从 而截断流体，反之即呈现通孔，供介质通过。球体的内腔为介质提供了小阻力、全通径的流道。
The ball valve trim is a sphere shape with a round hole passes the valve stem, when the ball rotates 90 degrees, the inlet and outlet port will shows a spherical surface, and becomes a flow channel when it rotate back. The spherical inner cavity provides a small resistance and full port for medium.