The Need Valve offers an axisymmetric shape and design of double seal of metal and elastic material which gives the water flow the space to always annular in the valve cavity. It shrinks to the axis at the outlet to avoid throttling to eliminate damage to the pipe network and piping caused by cavitation and vibration. The Needle Valve has an ideal geometric design, the fluid is well guided inside the streamlined valve body. Even in the case of high pressure difference. The valve can also effectively eliminate the high pressure difference, the high pressure reduced to low pressure, and will not produce vibration and cavitation occurrence. The continuous decreasing area of the annular runner from the inlet to the shrinkage section leads to the gradual increase of the flow rate without cavitation, and does not produce the energy conversion of cavitation damage. Whether the piston is in any position, the shrinkage section is annular, ensuring perfect linear adjustment characteristics.