Abstract: With preudanabaena sp., the common algae in raw water, as research object, the removal efficiency of preudanabaena sp.and the metabolized odor and taste compound, 2-MIB was studied by using Al³⁺ coagulation.The results show that the optimal dosage of Al³⁺ is 3 mg/L.Meanwhile, pre-oxidation with potassium permanganate and sodium hypochlorite were applied in order to enhance the coagulation.It is observed that low concentrations of potassium permanganate has no significant effect on coagulation while the peroxidation exhibits negative impact on the coagulation when MnO₄^- is increased to 2 mg/L, and the pre-oxidation with sodium hypochlorite even leads to the release of intracellular 2-MIB.Three-dimensional fluorescence data indicates that pre-oxidation process leads the release of intracellular organisms by cell lysis, which will have effect on the coagulation.