The invention discloses a method for secondary aluminum ash harmless use. The method comprises the following steps: mixing water with secondary aluminum ash, heating, stirring, leaching, and carryingout solid-liquid separation after water leaching so as to obtain primary filtrate and primary filter residues; heating and evaporating the primary filtrate so as to obtain a soluble salt; mixing the primary filter residues with an acid, heating and stirring to achieve leaching; after acid leaching, and carrying out solid-liquid separation so as to obtain secondary filtrate and secondary filter residues; manufacturing bricks with the secondary filter residues; adjusting the pH value of the secondary filtrate within 2.5-3.0; heating and aging the secondary filtrate after the pH value is adjusted, thereby obtaining aluminum polychlorid. By adopting the method, the aluminum element in secondary aluminum ash can be utilized to the maximum extent, aluminum nitride which is hard to react with theacid can be converted into aluminum hydroxide which is easy to react with the acid through high-temperature water leaching, dissolution of the aluminum element in the secondary aluminum ash can be improved, and the content of aluminum oxide in a prepared aluminum polychlorid product can be increased; in addition, a salt solvent and a nitrogen element in the secondary aluminum ash can be recycled,and damage of leaching residues upon the environment can be reduced.