The effluent quality of combined process containing O₃-BAC treatment between sedimentation process and dissolved air flocculation(DAF) process for the treatment of East Taihu Lake raw water were compared. The results showed that the removal efficiency of turbidity by DAF was 10.1％ higher than that by sedimentation process, and the effluent turbidity was stabled at 1 NTU or less after the treatment of the O₃-BAC. Compared with the sedimentation process, the CODMnand DOC removal efficiencies of DAF were increased by 5.4％ and 1.6％, respectively. The CODMnand DOC were stabled at 0.5-2.1 mg／L and 0.3-2.0 mg／L after O₃-BAC process respectively, while the organic concentration could not reach to effluent standard after conventional treatment. O₃-BAC process played a dominant role in the decrease of fluorescence intensity, while conventional treatment process had only a slight or no effect on the removal of fluorescent material. The experimental results indicated that the DAF was slightly better for algae removal efficiency than sedimentation process. The concentration of diatom activity and chlorophyll decreased to 0 and cyanobacteria still retained part of the activity after advanced treatment.