Abstract Removing red tide organisms with clays is a promising method used to control red tide in the world. This article reviewed our study on red tide prevention with clays in the last few years, which mainly included: (1) Coagulation and mechanisms of clays on red tide organisms. The effects of a series of factors, such as clay kinds and concentration, red tide species, pH value etc. on coagulation were investigated. (2) Preparation of modified clays and coagulation mechanisms. A theoretical model based on study on the coagulation of red tide organisms with clays was established, which showed that the surface modification of clays affected the coagulation and was the main way to improve the capability for clays to remove red tide organisms. Several methods were proposed to prepare the modified clays such as adding PACS (polyhydroxy aluminum chloride) in clays, preparation of positively charged clays by ways of insertion and surface adsorption. (3) Study on the kinetics of clays and modified clays removing red tide organisms. A model of the kinetics of red tide organisms coagulation with clays was established, which theoretical addressed the factors affecting the coagulation rate and suggested ways to increase the coagulation rate. The effects of different kinds and concentration of clays, of the second component PACS and MMH (mixed metal layered hydroxide) and of pH on the coagulation rate were examined. (4) Research on other aspects, including the study of main nutrient adsorption on clays in seawater, and impact of clays on growth of red tide organisms and production of algal toxin. Finally, the problems needed to be resolved in the study of red tide prevention with clays were raised and some suggestion was proposed to the future study in this area. null