NOVELTY - The device comprises a microbiological fuel cell stack, a single anode chamber (10) and a cathode chamber (2). The anode chamber is equipped with an anode solution and domesticated mature polyculture to generate microorganism flora set on the ground. The anode chamber cover is provided with a fixing wire (5) and a salt bridge (6). A cathode is set in the cathode chamber. A wall of the cathode chamber is provided with polluted underground water (4). The polluted underground water passes through a small hole on a cathode chamber.    USE - The device is useful for in-situ repairing contaminated underground water.    ADVANTAGE - The device allows in-situ repair of contaminated underground water without pollution in an economical manner.    DETAILED DESCRIPTION - The device comprises a microbiological fuel cell stack, a single anode chamber (10) and a cathode chamber (2). The anode chamber is equipped with an anode solution and domesticated mature polyculture to generate microorganism flora set on the ground. The anode chamber cover is provided with a fixing wire (5) and a salt bridge (6). A cathode is set in the cathode chamber. A wall of the cathode chamber is provided with polluted underground water (4). The polluted underground water passes through a small hole on a cathode chamber provided with a fixing wire and a salt bridge along a transfer path. The polluted underground water contains potassium chloride and agar. A branch pipe is a soft plastic pipe as the salt bridge. One end of the salt bridge is extended below the liquid level to the anode solution in the anode chamber by the salt bridge on the chamber. The salt bridge and branch pipe are respectively inserted into each of the liquid level in the cathode chamber. A load resistance of an electrical appliance is connected to one end of the anode chamber by fixing wire on the cathode chamber. The cathode chamber is connected with a lead by a silica gel pad. The anode chamber and the cathode chamber are sealed. The anode and the cathode are made of carbon cloth, carbon felt or carbon brush. The anode contains sodium and/or glucose as carbon source. A chemical oxygen demand of the anode liquid is more than 400 mg/l. The polluted underground water is capable of receiving electronic oxidizing material of nitrate and/or heavy metal chromium. The cathode chamber is reached to the discharge standard.    DESCRIPTION OF DRAWING(S) - The figure shows a schematic view of a device for in-situ repairing contaminated underground water.    Cathode chamber (2)    Polluted underground water (4)    Fixing wire (5)    Salt bridge (6)    Single anode chamber. (10)