Eutrophication with a large number of commonly occurs worldwide, thereby threatening the aquatic ecosystem and human health. In this study, four kinds of algicides were tested to explore their influence on cell density and chlorophyll-a of . Results showed that aluminum silicate agent, which inhibited more than 90% cell growth compared with the control group, demonstrated the strongest inhibition effect immediately on growth. Furthermore, the production and release of microcystin (MC)-LR were investigated. Aluminum silicate, CuSO , and Emma-11 were more effective than pyrogallic acid in disrupting the cells of , thereby increasing the extracellular MC-LR concentration. Aluminum silicate caused the highest extracellular MC-LR concentration of more than 45 mg·L . Biotoxicity was also detected to evaluate the environmental risks of MC-LR release, which were related to the usages of different algicides. Extracellular MC-LR concentration mostly increased when the biotoxicity of algae solution increased. The experiments were also designed to reveal the effects of physical conditions in riverways, such as natural sunlight, aeration and benthal sludge, on MC-LR degradation. These findings indicated that UV rays in sunlight, which can achieve a MC-LR removal efficiency of more than 15%, played an important role in MC-LR degradation. Among all the physical pathways of MC-LR removal, benthal sludge adsorption presented the optimal efficiency at 20%.