Abstract: In order to improve filtering effect of poly aluminium chloride（PAC），the influences of reaction time，filtering temperature，dosage of Ca（AlO2）2，contents of SO42-，Fe3+ ，and Al2O3 ，and basicity on PAC filtering effect were investigated from three aspects of process，raw materials，and product.Results showed that reaction time，filtering temperature，dosage of Ca（AlO2）2，and SO42- content in the raw material all had remarkable influence on filtering effect of PAC.To ensure filterability of PAC，reaction time of 60 min and filtering temperature at 60~80 ℃ were suggested，dosages of Ca（AlO2）2 and SO42- in acid were less as far as possible.Changes of Al2O3 content in the product had certain influence on filtering effect of PAC，but would not change filterability of PAC.Changes of Fe3+ in raw materials and basicity of PAC had no significant influence on filtering effect of PAC.

Key words: poly aluminium chloride, filtration performance, water insolubles