The invention relates to a method for promoting sludge to be reduced by ozone, in particular to a technology used for pretreating the sludge and accelerating anaerobic sludge digestion speed by utilizing ozone oxidation technique, which is widely applied to the sludge treatment technique of a sewage plant. The method comprises: the residual sludge of the sewage plant is concentrated and then treated by a sludge pretreatment reactor; due to the strong oxidizing property of ozone, the cell wall and the cell membrane of microorganism inside the sludge are broken, and a great deal of organic matter is released out of cells; after being treated by the ozone, the sludge enters into an anaerobic digestion reactor, and anaerobic digestion can be carried out in a closed anaerobic state; gas generated by digestion is treated by a gas purifying device, and methane can be obtained; after anaerobic digestion, the sludge is treated by flocculation and dehydration, and dewatering sludge can be obtained; then, final treatment can be carried out, for example, the sludge can be used for manufacturing agricultural fertilizer, bricks, porcelain granules or auxiliary fuel of fire coal; and anaerobic supernate is treated by biological filtering bed technique, so that the organic matter, ammonia and nitrogen in the solution can be removed.