The invention discloses a method for preparing sludge concrete. The method for preparing the sludge concrete comprises the following steps of: weighing the following raw materials in percentage by weight: 1% of ocean sludge, 1-4% of caustic sludge, 0.5-5% of mineral powder, 1-3% of powder coal ash, 0-20% of pebbles, 0-9% of limestone and the like as well as 0.5-3% of catalyst based on the total weight of the above raw materials, wherein the catalyst can be a naphthalene-based superplasticizer, an early-strength slushing agent and the like; and the ocean sludge is obtained by means of grabbing and piling up. The method for preparing the sludge concrete comprises the following steps of: adding all the raw materials into a stirring machine in percentage by weight, and mixing uniformly to obtain a mixture; and standing the mixture for no more than 10 hours according to the water content and the environment temperature so that the mixture reacts fully, thus obtaining the sludge concrete which can be used directly. The method provided by the invention has the advantages of shortening the working period, saving expense, and recycling the sludge and industrial waste slag residues, is rapid in solidification speed, is good in effect, can realize sustainable development of environment-friendly economy and regenerated energy sources, can be applied to pavement concrete, prefabricated blocks, cement stabilizing layers, surface protecting block bodies and the like in municipal administration, traffic, water conservancy and port engineering.