The invention belongs to a wellhead blowout prevention device used for an rod oil-pumping well and particularly relates to an oil field wellhead blowout prevention device. An upper sealing cavity anda lower sealing cavity are formed in a sealing box fixedly connected to a wellhead, a working cylinder is connected into a seat hole in the lower end of a sealing box base through a thread, the interiors of the upper sealing cavity and the lower sealing cavity in the sealing box are matched with a polish rod through an upper sealing filler and a lower sealing filler, an upper end marker and a lower end marker are arranged on the polish rod, the lower end of the polish rod is connected with a working plunger, and the lower end of the working plunger is connected with a standby plunger through aconnecting rod, wherein the diameter of the working plunger is greater than that of the polish rod, the working plunger and the standby plunger are matched with the working cylinder, and the diameterof the connecting rod is equal to that of the polish rod. The oil field wellhead blowout prevention device is reasonable in structure and reliable in performance and can seal the wellhead enduringly,the pressure-bearing load of the upper stage of rubber packing is reduced, the upper stage of sealing piece can be replaced or a wellhead device can be overhauled in a controllable state, sewage-discharging emptying is avoided, and safe, efficient, environment-friendly and energy-saving production is achieved.