The invention belongs to methods and equipment for treating sludge and particularly relates to a method for treating nutrient substances in excess sludge and a special high-voltage alternating-current pulse sludge decomposition device. The nutrient substances in the excess sludge are treated through the technological steps of thermal refining, sludge wall or film breaking, mud and water separation, injection of supernate into a biochemical system and the like. The high-voltage alternating-current pulse sludge decomposition device comprises a sludge flowing pipe, connection flanges arranged at the two ends of the sludge flowing pipe, a sludge inlet, a sludge outlet, electrodes arranged in the sludge flowing pipe, and a power source electrically connected with the electrodes, wherein the sludge inlet and the sludge outlet are formed in the front part and the rear part of the sludge flowing pipe. The number of the electrodes is at least two, the electrodes are evenly distributed in the sludge flowing pipe, and a high-voltage alternating-current pulse power source is selected as the power source. The method for treating the nutrient substances in the excess sludge and the special high-voltage alternating-current pulse sludge decomposition device solve the problems that in the prior art, an additional carbon source exists, a large amount of manpower and material resources are needed, the operation burden and cost of a sewage plant is aggravated, the reagent dosage is large, and operation is complex. The method for treating the nutrient substances in the excess sludge and the special high-voltage alternating-current pulse sludge decomposition device have the advantages that energy consumption is low, the sludge treating effect is good, and the carbon source dosage is small.