Standard jar tests were conducted to evaluate the effectiveness of ferrate preoxidation in enhancing the coagulation of surface waters. A substantial reduction of residual turbidity after sedimentation and filtration was achieved by ferrate preoxidation in all cases of the investigation of various water qualities at low ferrate dosage (0.5-1.0 mg/l). The enhancement of the coagulation was more obvious when the organic content in the waters were relatively high.