The invention discloses a method for optimizing a SNCR (selective non-catalytic reduction) denitrification system of a garbage incinerator by adding an anionic surfactant. The method comprises the step of adding a certain amount of anionic surfactant in an ammonium water diluting process based on the existing SNCR denitrification method. After the anionic surfactant and an ammonium water solution are mixed and sprayed to a hearth, the mixture is decomposed at high temperatures to generate active free radicals such as -OH, so that the reaction efficiency and time of atomized ammonium water drops and NOx in smoke are effectively ensured, the integral denitrification efficiency of the SNCR system is improved, the optimum reaction temperature region is expanded, and moreover, no adverse influence is brought to stable combustion of the incinerator. Compared with the existing SKCR denitrification compound additives, the method disclosed by the invention is simple in process, single in additive and low in cost, and thus is a method which can effectively improve the SNCR denitrification efficiency of the garbage incinerator and has a relatively broad application prospect.