The invention relates to a method for settling and purifying coal slurry water through electrolysis, which comprises the steps of selecting chemical substances, preparing an electrolyte and a flocculating agent and carrying out electrolysis for settlement and purification with power supplied by a 36V DC powder supply, wherein the flocculating agent is polyacrylamide, the electrolyte is aluminum chloride or magnesium chloride, and sodium chloride, ferric chloride, aluminum sulfate and calcium oxide, deionized water is used as a solvent, sodium hydroxide is used as an alkalinity adjusting agent, a graphite tube is used as an anode, a stainless steel electrolytic cell is used as a cathode, the coal slurry and water are separated through the DC powder supply electrolysis, stirring and combination reaction, the turbidity of water obtained after separation is 8.92NTU, the coal slurry grains are round and smooth and loosely piled, and compared with the prior art, the sedimentation speed is increased by 20 percent, the turbidity is reduced by 16 percent compared with the prior art, and the use of the polyacrylamide is reduced to 23 grams for per ton of raw coal. Therefore, the method is an ideal method for settling and purifying coal slurry water, represents the first like technology in China, and can be widely promoted and used in the technical field of coal dressing.