NOVELTY - Double-chamber algal microorganism fuel cell comprises reactor box (13), wire (14), external circuit (15), anode (3), cathode (4), cation exchange membrane (5), air conduit (7) and air collector (8). The cation exchange membrane is vertically set in reactor box in which anode chamber (1) and cathode chamber (2) are arranged; anode arranged in anode chamber and cathode arranged in cathode chamber; air collector arranged at the air outlet (16) in sealing manner; both anode chamber and cathode chamber comprising organic glass; and algal microorganism added in cathode chamber.    USE - Double-chamber algal microorganism fuel cell.    ADVANTAGE - The fuel cell achieves CO2-free drainage and can recycle electric energy.    DETAILED DESCRIPTION - Double-chamber algal microorganism fuel cell comprises reactor box (13), wire (14), external circuit (15), anode (3), cathode (4), cation exchange membrane (5), air conduit (7) and air collector (8). The cation exchange membrane is vertically set in reactor box in which anode chamber (1) and cathode chamber (2) are arranged; anode arranged in anode chamber and cathode arranged in cathode chamber; two ends of the wire pass through upper cover plate (13-1) of reactor box to connect anode and cathode; external circuit arranged outside reactor box and connected with wire; upper cover plate of the reactor box above anode opened with air collection chamber (6); one end of the air conduit (7) in sealed connection with air collection chamber while other end passes through upper cover plate of reactor box (13) to be arranged at the bottom of the cathode chamber; air collector arranged at the air outlet (16) in sealing manner; both anode chamber and cathode chamber comprising organic glass; and algal microorganism added in cathode chamber. An INDEPENDENT CLAIM is included for a method of utilizing double-chamber algal microorganism fuel cell for treating wastewater and realizing carbon dioxide (CO2)-free drainage, comprising respectively injecting domestic sewage or anode water of microorganism fuel cell into anode chamber and cathode chamber, adding alga with inoculation concentration of 0.3-1 g/L in cathode chamber, utilizing microorganism in domestic sewage to start double-chamber algal microorganism fuel cell, leading CO2 generated in anode chamber into cathode chamber to be absorbed by alga for photosynthesis, when the cell voltage is lower than 50 mV, completely changing the domestic sewage in anode chamber until load voltage is stabilized above 530 mV, to finish starting of algal microorganism fuel cell; and injecting wastewater in anode chamber and cathode chamber, metabolizing microorganism at room temperature to generate organic matter and obtain electric energy, and leading CO2 generated in the anode chamber into the cathode chamber to receive photosynthesis of alga on the cathode, when electric potential of the anode higher than - 50 mV, totally draining wastewater treated by anode chamber and injecting new wastewater, when the electric potential of the cathode is lower than 30 mV, totally draining wastewater treated by the cathode chamber (2) and injecting new wastewater.    DESCRIPTION OF DRAWING(S) - The drawing shows a cross-sectional view of the double-chamber algal microorganism fuel cell.    Anode chamber (1)    Cathode chamber (2)    Anode (3)    Cathode (4)    Cation exchange membrane (5)    Air collection chamber (6)    Air conduit (7)    Air collector (8)    Reactor box (13)    Upper cover plate (13-1)    Wire (14)    External circuit (15)    Air outlet (16)