The wellhead valve is an important component in many wellhead assemblies, such as BOP well-control assembly, production test assembly, water injection assembly and the like. All the valves belong to parallel ram style or wedge ram style and their koints belong to threaded, flanged or clamped-in style. (show in chart). All the designs of valves match up to the Spce. API6A. The valve body and valve lid adopt metal-and-metal sealing, while valve ram and valve seat adopt metal or nonmetal sealing according to client's requirements. Carbide is wielded on all sealing surface in possession of erosion and corrosion resistance. The space between valve stem and valve lip is installeda back-off sealing unit for the convenience of replacing valve atem and stuffing under pressure. The parallel ram and spring pre-load valve seat is real bi-directional sealing with low operation torque.