The invention provides a single double-needle valve double-nozzle high-pressure common rail oil injector for a medium-heavy diesel engine. The single double-needle valve double-nozzle high-pressure common rail oil injector comprises a magnetic core valve seat, a ball valve ejector rod base mounting screw cap, a ball valve ejector rod base, a valve needle control rod base, an oil nozzle mounting screw cap and an oil nozzle valve body; two electromagnetic valves are arranged in the magnetic core valve seat, two valve needle control rods are arranged in the valve needle control rod base, two valve needle cavities are formed in the oil nozzle valve body, two oil nozzles are arranged at the lower ends of the valve needle cavities, and two oil nozzle valve needles which are connected with the two valve needle control rods and are used for controlling the two oil nozzles are arranged in the valve needle cavities. In addition, a ball valve ejector rod and a high-pressure sealing ball valve arearranged in a split mode, and the ball valve ejector rod is designed into a large-diameter section and a small-diameter section, so that the needed electromagnetic force is further reduced. The function of the high-pressure common rail oil injector is more suitable for a diesel engine to inject diesel oil compared with a traditional oil injector, under the condition that the pressure of a fuel system is not increased, the atomization effect of high-pressure diesel injection can be further improved, and the emission level of an engine original machine can be improved; and meanwhile, the oil spraying rate rule is optimized, and the power level of the diesel engine is further explored.