The quality of eutrophic waters was improved by the algae-bacterium biofilm, which covered over the artificial aquatic mat made from a kind of mend macromolecule material. Two series of experiments show that using the artificial aquatic mat technique, algae bloom was inhibited markedly. At the eleventh day, the transparency was increased from 6 cm to 62 cm; and the concentrations of CODMn, TP, TN and NH4+-N were decreased to 92.89%, 49.25%, 94.97% and 70.15% respectively. The DO concentration also kept in certain satisfied level for using the algae-bacterium biofilm method. The suitable and economical density was about 8 similar to 16 bunchs/m(2) when the ratio of the artificial aquatic mat length to water depth was 0.7.