The invention discloses a method for preparing green-energy fuel by mixing agricultural wastes and sludge. The method takes the agricultural wastes and the sludge as raw materials and the raw materials are treated through a process of crushing, drying, mixing, sieving and the like to prepare the final green-energy fuel. In a combustion process of the prepared green-energy fuel, a sludge componentis converted into a hydrocarbon compound through a high-temperature effect and the hydrocarbon compound can be used as excellent auxiliary fuel to provide certain combustion heat; components of the agricultural wastes have excellent combustion performance; in a combustion process, a lot of heat is released; residues after combustion can be directly used as a soil improvement agent and fertilizer,and composting treatment is not needed, so that damages to the environment are avoided.