The invention discloses a method for manufacturing ecological building blocks of a riverway protection slope from sewage plant sludge, belonging to the technical fields of resource utilization and environmental protection. The method comprises the following steps of: uniformly mixing and stirring sludge, cement, gravels, sand and water of a sewage plant; and prepressing and forming under a certain pressure and culturing under the steaming and curing condition to manufacture ecological protection slope building blocks for riverway renovation. The invention can solve the problems of sludge disposal and treatment, solves the problem of secondary pollution of heavy metals and pathogens in sludge and realizes the renewable resource recycling of the sludge. The produced ecological building blocks have the advantages of high strength and blush resistance, and N, P and K in the sludge can be used as nutrition matrixes for ecological growth, thus the ecological system of the riverway protection slope can be improved and a favorable riverway landscape is built.