The invention discloses a method for preparing an environmentally friendly brick. The technical proposal includes: pouring a certain amount of rice husk, sawdust and rubber particles into a certain amount of sewage, adding sludge produced by Fenton oxidation, biochemical sludge and powder Coal ash, stirring to obtain a mixture A of rice husk, sawdust, rubber particles, sludge produced by Fenton oxidation, biochemical sludge and fly ash, transfer the mixture A to a hydrothermal reactor, control the reaction temperature and time, and naturally Cool, filter off the supernatant to obtain mixture B and supernatant; weigh a certain amount of mixture B, add a certain amount of supernatant, and add polypropylene fiber and cement to it, stir and filter to obtain mixture C; The mixture C is transferred to a brick-making mould, which is subjected to compression molding and steam curing to obtain an environmentally friendly brick. The environmentally friendly brick includes porous carbide, iron oxide, harmless sludge, fly ash polypropylene fiber, and cement. It has the advantages of light weight and high strength, reaching MU25 grade.