A series of poly-aluminum-chloride-sulfates (PACS), which have different OH/Al (┌) and Al3+/SO42- mole ratios, has been prepared using AlCl3-6H2O, Al(SO4)3-18H2O and Na2CO3 as raw materials. The electrophoretic nature of PACS was investigated by electrophoresis. Laboratory experiments were undertaken to evaluate the PACS in comparison with polyaluminum chloride (PAC) for the coagulation of simulating water and actual wastewaters. The experimental results show that the ┌ value and the Al3+/SO42- mole ratio affect the electrophoretic nature of PACS. PACS has a maximum zeta potential at about a ┌ value of 1.5 and Al3+/SO42- mole ratio of 12- 16. The zeta potential of PACS varies with pH. The performance of PACS as coagulant is affected by ┌ value and Al3+/SO42- mole ratio. PACS of ┌＝2.1 and Al3+/SO42-＝15 gives best turbidity removal effectiveness. In comparison with PAC of ┌＝2.0, PACS of ┌＝2.0 and Al3+/SO42-＝16 gives higher removal efficiency for turbidity and COD, and shows the following advantages in the clarification of waters andwastewaters: rapid aggregation velocity, larger and heavier flocs, and lower required dosage.