Abstract: <FONT face=Verdana>BPFS (bio-polyferric sulfate) was prepared by introducing biological technique to polyferric sulfate production.In order to strengthen the oil removal performance of BPFS,nano-sized Fe3O4 and superfine Fe2O3 power were prepared,then combined with BPFS to treat oily wastewater,respectively.Oil removal performances of the two sets of complex coagulant were investigated.Results showed that the treatment effect of the complex coagulants on treating oily wastewater was superior to single BPFS and the treatment effect of nano-sized Fe3O4/BPFS complex coagulant was superior to that of Fe2O3 power/BPFS.On treating mini-oily wastewater,the optimal addition dosages of superfine Fe2O3 power and nano-sized Fe3O4 were 3 mg/L and 2 mg/L,respectively,and the highest oil removal rate could be up to 94.8%.</FONT>