Alcaligenes eutrophus was successfully recovered from high cell density broth by pre-treatment with Fe-based coagulants. An inorganic coagulant, Fe2(SO4)3, and a polymerized coagulant, Ferix-3, were used. Good coagulation was observed in broad pH range of 3 to 13, the floc size was increased with increasing pH of culture broth. The optimum pH of fermentation broth for cell recovery was 10 to 13. The optimum coagulant dosages to recover cells with 95% cell recovery were increased with increasing cell concentration. Optimal coagulant dosage was lower when the polymerized coagulant was used rather than the inorganic coagulant. The coexistence of NH4/+ was increased coagulant requirement, and the coagulant requirement was 0.066g Fe3+/g NH4/+.