Abstract: The coagulation-supporting effect of pre-oxidation of potassium manganate in the process of coagulation was studied in this paper.The experimental results showed that the coagulation-supporting effect of potassium manganate was obvious. When the dosage of potassium manganate was 2.0 mg/L,the turbidity removal efficiency of sedimentation water was 95.59%.However,when the dosage of Al₂(SO₄)₃ was 8.0 mg/L without adding potassium manganate,the turbidity removal efficiency of sedimentation water was only 88.61%.The neutral and weak alkaline water had good effect on coagulation-supporting effect of potassium manganate, except weak acid water.The Mn²⁺ in the water was helpful for potassium manganate to remove turbidity.Potassium manganate should be added before adding coagulant.Under the best potassium manganate dosage,the turbidity removal efficiency of sedimentation water exceeded 90.00% when the pre-oxidation time was 3 min.In addition,potassium manganate had good coagulation-supporting effect on high turbidity water.