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A series of poly-aluminum-chloride-sulfate(PACS) coagulants,which have different SO42-/Al3+ and OH/Al(γ) mole ratio,has been successfully developed using AlCl3·6H2O,Al2(SO4)3·18H2O andNa2CO3 as raw materials.The coagulation performance of PACS for removing natural organic matter (NOM) from actual surface water has been evaluated.The effect of SO42-/Al3+ mole ratio and γ value in coagulants PACS on DOC and UV254 removal was examined.And the influence of pH and dosages of selected PACS with SO42-/Al3+ ratio of 0.0664 and γ value of 2.0,which achieved the best coagulation performance forremoval of DOC and UV254 than other coagulants PACS,on the removal of DOC and UV254 and residual aluminum concentration in treated water was also examined in comparison with polyaluminum chloride (PAC) with γ value of 2.0.The experimental results show that the performance of PACS as a coagulant was highly dependent on SO42-/Al3+ mole ratio and γ value.Both for the selected PACS and for PAC,the best DOC andUV254 removal results were obtained in the range of pH from 5.0 to 8.2 and at the coagulation dose of 5.0mg/L as Al.Under the optimum coagulation conditions,the selected PACS gave higher DOC and UV254removal efficiency,and lower residual aluminum concentration in the treated water than PAC.The maximumremoval of DOC and UV254 for PACS was approximately 88.0 ％ and 93.0 ％,respectively.At the optimumcoagulant dose and pH 6.5,the concentration of residual aluminum in treated water by both selected PACSand PAC can comply with the regulated limits.The major mechanisms of NOM removal by PACS and PACcoagulation involve complexation-charge-neutralization-precipitation.