The invention relates to light-weight foamed ceramic having a surface with a heavy metal ion exchange function. The provided ceramic is formed by growing an activated layer having a heavy metal ion exchange function, such as a Prussian blue activated layer, on a light-weight foamed ceramic surface. The light-weight foamed ceramic is low-density porous ceramic the macroscopic porosity of which is at the millimeter level and has a large surface area; and the activated layer formed on the surface has the good metal ion exchange function, and can effectively remove toxic heavy metal ions in water body, and therefore an efficient heavy metal ion adsorption material can be formed by combining the light-weight foamed ceramic and the activated layer and can float on the water surface. The porous composite material is formed by adopting the light-weight foamed ceramic prepared by adopting natural zeolite powder as a main raw material as a matrix, and by a step of directly growing the activated layer having the heavy metal ion exchange function on the ceramic surface through an interfacial reaction in a solution.