Polyacrylamide is divided into four types: anionic, cationic, nonionic and zwitterionic. The parameter index in each polyacrylamide is also different, so its action basis and effect will be different. The charges in wastewater from different industries are also different, and different types of polyacrylamide are required to treat the effect. This is also the main reason why polyacrylamide needs to be selected.