Polyaluminum chloride (PAC) is an inorganic substance, an emerging water purification material, inorganic polymer coagulant, referred to as polyaluminum. It is intermediate between AlCl3and Al (OH)3A water-soluble inorganic polymer with the chemical formula [Al2(OH)nCl6-n]m, where m represents the degree of polymerization and n represents the degree of neutrality of the PAC product. n=1~5 is a high-charge polymeric ring chain with Keggin structure, which has a high degree of electrical neutralization and bridging effect on colloids and particulate matter in water, and can strongly remove microtoxic substances and heavy metal ions, and has stable properties. The inspection method can be inspected according to the national standard GB 15892–2003 standard. Due to the bridging effect of hydroxide ions and the polymerization of polyvalent anions, the polyaluminum chloride produced is an inorganic polymer water treatment agent with relatively large molecular weight and high charge.