To study the effects of attached bacteria on the microenvironment of Microcystis cells of blooms, thirty-four attached bacterial strains were isolated from Microcystis colonies sampled from 4 different bloom samples, and enzyme-producing abilities of the isolated strains were measured. Measuring of nitrogen metabolism enzymes showed that 13 strains could hydrolyze casein, 5 strains could effectively remove ammonia, and 1 strain had a strong nitrate reductase activity. Measuring of phosphorus metabolism enzymes displayed 4 strains with phosphates' activity. The measurement also showed 11 strains with esterase activity. To evaluate the effects of the bacterial strains on the growth of Microcystis, each isolated strain was co-cultured with Microcystis. The results showed that 11 strains could obviously promote Microcystis growth,took up 32% of the total isolates; three strains obviously inhibited the growth, took up 9.9% of the total isolates. Relationship of enzyme production ability and effects on Microcystis growth revealed that the growth-promoting strains were case in aseor esterase-producing strains.