Abstract: The frequency and intensity of freshwater bloom grow worse as the pollution and eutrophication of fresh waters become more and more serious. The recent study of microcystins is present, which is the main secondary metabolites produced by toxic bloom. This toxin is a class of monocyclic heptapeptides with many different isomerides. It has become potential hazardous material in aquatic environments for its toxic, distribution and stability. The fate of microcystins also became the focus of research. As the risk factor of safe assessment, the main assay methods are HPLC and enzyme-linked immunosorbent assays (ELISAs). The control methods using physical, chemical and biological ways have been developed to improve the water supply quality. The trend of research about microcystins is discussed based on the situation of China, which is an urgent need to the restoration of the large eutrophicated lakes.