The invention provides hyperbranched polyamide modified chitosan quaternary ammonium salt which is obtained through the reaction of hyperbranched polyamide, chitosan and alkyl halide.The hyperbranched polyamide is prepared from trimesoyl chloride and ethylenediamine through a solution polymerization method.The alkyl halide comprises methyl iodide, ethyl iodide, methyl bromide or ethyl bromide.The microsphere prepared from the quaternary ammonium salt is applied to treatment of methyl orange wastewater, the final dye removal rate can reach 99.67%, the microsphere is renewable, and the preparation process is simple and free of pollution.