The invention discloses a method for preparing 3,5-dichloroaniline. The method comprises the following steps of: (1) dissolving 2,4-dichloroaniline in hydrochloric acid or sulfuric acid to form 2,4-dichloroaniline hydrochloride or sulfate, dropwise adding bromine at room temperature while stirring, thereby obtaining the hydrochloride or sulfate of 2-bromo-4,6-dichloroaniline; (2) adding ethanol or isopropanol to the hydrochloride or sulfate reaction liquid of 2-bromo-4,6-dichloroaniline obtained in the step (1), cooling to about 0 DEG C, dropwise adding the aqueous solution of sodium nitrite, continuing stirring for 30-50 minutes after dropping, slowly increasing the temperature until boiling, and evaporating out 3,5-dichlorobromobenzene for future use; and (3) adding ammonia water and a catalyst to the 3,5-dichlorobromobenzene obtained in the step (2) for reacting for 3-6 hours at the temperature of 130-180 DEG C, thereby obtaining 3,5-dichloroaniline. The method provided by the invention has the advantages that raw materials are easily available, reaction is simple, conditions are mild, yield is high.