A flagellate Jin821 which could feed on toxic cyanobacteria Microcystis aeruginosa was isolated, and it was identified as a species of golden alga according to its morphological characters and 18S rDNA genes. The results of feeding experiments showed that the golden alga Jin821 could make the high density (4.3x10(6) cells.mL(-1)) of M. aeruginosa clear in a short time (40 h), with a removal rate of 99.9%. And the microcystin (MC-LR) was also degraded effectively at the same time, with a removal rate of 82.7% of 114 microg/L in 40 h. The growth curve of Jin821 was in 'S' style, with four phases of lag, log, stationary and decline. When M. aeruginosa was cleaned out, Jin821 would decline in number and slowed down in movement. In summary, the golden alga Jin821 can be a potential biological way to control blue algal blooms in the future.