The invention discloses a method for preparing a porous suspension water treatment material. The method comprises the following process steps: putting coal ash ceramsite into a sodium silicate and sodium phosphate solution, carrying out ultrasonic cleaning, drying, and calcining so as to obtain modified coal ash ceramsite; preparing a solution from absolute ethyl alcohol, tetrabutyl titanate, tributyl borate, acetylacetone, polyethylene glycol 300, an emulsifier NP-7, deionized water and lanthanum nitrate, adding the modified coal ash ceramsite, and stirring so as to obtain a gel substance; drying and calcining the gel substance, thereby obtaining the porous suspension water treatment material. The porous suspension water treatment material prepared by using the method has the characteristics of being low in density, high in strength and high in air porosity, and in addition organic matters can be decomposed by a photocatalyst membrane on the surface of the material, so that functionsof purifying sewage and cleaning the surface of the ceramsite can be achieved.