Abstract: The secondary aluminum dross still contains a large amount of metallic aluminum, and its recycling is of great significance. In this paper, secondary aluminum ash was used as the raw material. After treating it by hydrochloric acid leaching, calcium aluminate was then added to prepare polyaluminum chloride (PAC). The influencing factors such as the concentration of HCl, leaching temperature, time, liquid-solid ratio, and calcium aluminate addition amount were mainly investigated. The best conditions for preparing polyaluminum chloride by acid leaching of secondary aluminum dross were as follows: the secondary aluminum dross after washing was leached at the HCl concentration of 6 mol/L, the liquid-solid ratio of 4∶1 mL/g, at 85 ℃ for 2 h, and then added calcium aluminate 12 g/80 mL to the acid leaching solution and reacted at 85 ℃ for 1.5 h. Under these conditions, the leaching rate of aluminum during the acid leaching process was 48.67%, and the liquid PAC prepared was fully compliance with the national standard.