The invention discloses a hydrotalcite-poly(m-phenylenediamine) composite material and a preparation method and application thereof. The hydrotalcite-poly(m-phenylenediamine) composite material comprises hydrotalcite and poly(m-phenylenediamine), which is loaded on the surface of hydrotalcite. The preparation method comprises the steps as follows: preparing a dispersion of hydrotalcite and m-phenylenediamine; and mixing the dispersion of hydrotalcite and m-phenylenediamine with an oxidant for oxidative polymerization. The hydrotalcite-poly(m-phenylenediamine) composite material has the advantages of low cost, easy synthesis, good adsorption performance and the like. The preparation method has the advantages of simple process, convenient operation, mild reaction condition, low cost, high production efficiency, short production cycle, high product yield, is suitable for large-scale preparation, and is conducive to industrialized application. The composite material of the invention can beapplied to the treatment of diclofenac wastewater, and has the advantages of simple process, convenient operation, low cost, high treatment efficiency and good adsorption effect, and has high application value and commercial value.