The invention discloses a device and a method for underground long-distance transmission of Manchester code (Man code), and belongs to the technical field of communication and the technical field of oil exploration. The device for the underground long-distance transmission of the Man code comprises a Man code sending unit and a Man code receiving unit. The Man code sending unit comprises a Man code encoding module, a bipolar pulse generating module and a push-pull driver module. The Man code receiving unit comprises an inductance-capacitance (LC) parallel resonant module, a unipolar pulse generating module, a Man code decoding module and a communication module. The Man code sending unit is used to compile data into a unipolar pulse and then generate a bipolar pulse, and the improved push-pull driver module is used to drive the bipolar pulse to be sent to a cable transmission unit. Appropriate inductance is selected in the Man code receiving unit and connected in parallel between a signal line of the receiving end of the cable transmission unit and a ground wire, LC parallel resonance is generated on the highest frequency component of Man code pulses, then the Man code unipolar pulse is generated, and the Man code unipolar pulse is decoded and transmitted to a host computer. The device and the method for the underground long-distance transmission of the Man code are suitable for an underground high temperature severe environment, the severe attenuation distortion drifting problem of single-ended signals in long-distance transmission can be resolved, and the unipolar pulse can be decoded correctly.