The invention provides a recyclable water purifying agent preparation method. The method includes: step 1, mixing polyether polyol, isocyanate, sodium dodecyl benzene sulfonate, carboxymethyl cellulose, dibutyltin dilaurate, aluminium hydroxide and ferroferric oxide magnetic powder to obtain a foam material; step 2, mixing butyl titanate, sepiolite powder, halloysite nanotubes, nanocrystalline cellulose, polyvinylpyrrolidone, ferroferric oxide magnetic powder and absolute ethyl alcohol to obtain a mixed liquid A; mixing a hydrochloric acid solution, absolute ethyl alcohol and water to obtain a mixed liquid B; dropwise adding the mixed liquid B into the mixed liquid A, and reacting to obtain sol; subjecting the sol to silver loading treatment; step 3, mixing the foam material, the silver-loaded sol and phenoxy resin to obtain a mixed foam material; ageing and cleaning to obtain wet sponge; step 4, drying and grinding the wet sponge to obtain a recyclable water purifying agent. The recyclable water purifying agent prepared according to the method is effective in adsorption, high in adsorption capacity, high in efficiency and recyclability.