<p>A shut-off valve for pipe comprises a valve body and a valve clack (2). A 90 degree change of direction is formed by a fluid inlet and a fluid outlet of the valve body. The bottom surface (21) of the valve clack (2) is a constraining plane which is convenient for the change of direction of the fluid from the fluid inlet to the fluid outlet. The constraining plane is a sphere. A supporting body (4) and a guiding device (3) are placed on a valve rod, and the axial movement of the valve clack is limited by the guiding device (3).</p>
