The invention provides a preparation method of a ceramisite filter material for water treatment, comprising the following steps: naturally air-drying sewage sludge and water supply sludge; respectively grinding and smashing clay and the air-dried water supply sludge and sewage sludge, and filtering by using a sieve after smashing; detecting the percentage contents of SiO2, Al2O3, Fe2O3, CaO, MgO, K2O, Na2O and organic matters in the clay, the water supply sludge and the sewage sludge: detecting the following chemical components in powder after mixing, and if a following ratio is not reached, adding absent substances, so that a mixture meets a certain ratio as follows; adding water in the mixture, stirring until a sticky state is formed, and then putting into a ball forming mill for ball forming, wherein the addition amount of the water is 36-44 percent of the weight of the mixture; putting a pellet at a cool and ventilated place, and naturally drying for 24h; putting the pellet into a muffle furnace, adjusting the temperature to 395-405 DEG C, and preheating for 10min; heating up for firing, and keeping a constant temperature for 20min after the in-furnace temperature of the muffle furnace is increased to 1200 DEG C; after completely firing the ceramisite filter material, taking out the ceramisite filter material, and naturally cooling to room temperature.