For the proposal of Microcystis aeruginosa control technique by coagulants, removal effects of coagulants were carried out using isolated strain and collected water bloom of M. aeruginosa on Downstream of the Nakdong River. Both of purified and field-collected M. aeruginosa were entirely sedimented by the addition of the coagulant ceramic-zeolite type Co 100 (1.5 mg/$ell$) within 24 hr, but Yellow loess (10 mg/$ell$) was less effective for the removal of M. aeruginosa within 24hr. Thus it was concluded that Ceramic-Zeolite type Co 100 was the most effective coagulant.