The efficiency of iron chloride on simultaneous denitrification and chemical-biological flocculation process was investigated through a lab-scale study. The results showed that: there were not significant differences in the denitrification rate, COD and NO3(-) -N removal efficiency between the control reactor and the denitrification reactor with the dosage of 20 mg x L(-1) Fe after 14 days' domestication. Meanwhile the TP removal efficiency was increased to over 80%. Though sludge concentration was increased by adding FeCl3, the settling performance wasn't change because the sludge density was increased and the particle size was reduced. The sludge settling volume (SV30) and specific resistance of filtration (SRF) after adding FeCl3 were only 22% and 1.5 x 10(12) m x kg(-1), which were lower than the values in the control reactor and benefit for sludge treatment.