A series of poly-aluminum-chloride-sulfates (PACS), which have different OH/Al (gamma) and Al(3+)/SO4(2-) mole ratios, has been prepared using AlCl3 x 6H2O, A(SO4)3 x 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 gamma value and the Al(3+)/SO4(2-) mole ratio affect the electrophoretic nature of PACS. PACS has a maximum zeta potential at about a gamma value of 1.5 and Al(3+)/SO4(2-) mole ratio of 12-16. The zeta potential of PACS varies with pH. The performance of PACS as coagulant is affected by gamma value and Al(3+)/SO4(2-) mole ratio. PACS of gamma = 2.1 and Al(3+)/SO4(2-) = 15 gives best turbidity removal effectiveness. In comparison with PAC of gamma = 2.0, PACS of gamma = 2.0 and Al(3+)/SO4(2-) = 16 gives higher removal efficiency for turbidity and COD, and shows the following advantages in the clarification of waters and wastewaters: rapid aggregation velocity, larger and heavier flocs, and lower required dosage.