The valve stem top end uses spray-welding wear-resistant alloy(or hard alloy material,and it can resist high pressure high speed liquid scouring.The connection between packing box and valve body is a union structure which is simmple and accessible.Turning of adjustable choke valve handwheel can drive valve stem to rotate, generating forward and backward movement,changing annular tapered surface gap between valve stem valve needle position and valve seat,therefore adjusting the flow.