Abstract: The compound flocculant CBF-737 (the compound of polyaluminum chloride (PAC) and biological MBF-737) was used to treat eutrophic landscape water in this study.Results showed that adding 1.8 mL compound flocculant CBF-737 (0.9 mL of 5 g/L PAC and 0.9 mL of 2.5 g/L MBF-737) , and 1.5 mL of 1% CaCl₂ to 100 mL eutrophic water, the optimal hydraulic conditions were as follows: quickly mixing speed of 280 r/min for 60 s, slowly mixing speed of 100 r/min for 45 s. The water turbidity, total phosphorus and residual aluminum were reduced from 58. 3 NTU, 1.94 mg/L and 0.383 mg/L to 2.98 NTU, 0.198 mg/L and 0.178 mg/L, respectively. Moreover, the removal ratio of algae almost reached 100%. Composite flocculant CBF-737 treatment of the eutrophic water coagulation mechanism was as follows: aqueous colloidal was combined with the —OH, —COOH group of MBF-737 by electrovalent bond; the PAC was rapidly hydrolyzed in the water, which could compress electric double layer and destroy the colloidal stability; and CaCl₂ as the nucleation material, solid flocs formed through the biological flocculation agent adsorption bridge and enmeshment action.