With the development of industry and the economy, water eutrophication and the resulting cyanobacterial blooms are becoming increasingly serious. Cyanobacterial blooms seriously affect the safety and health of the aquatic ecology. The formation process of cyanobacterial blooms includes four stages: dormancy, recovery, biomass increase and formation of macroscopic blooms. The growth mechanism of cyanobacteria itself is an important reason for the outbreak of cyanobacterial blooms, among which the buoyancy regulation mechanism of cyanobacteria is one of the most important survival strategies of cyanobacteria, which plays an important role in the recovery of cyanobacteria in spring, the massive growth of cyanobacteria in summer and the final rise to the water surface to form a bloom. Understanding the mechanism of cyanobacterial buoyancy regulation and its role in cyanobacterial blooms is of great importance for understanding the growth characteristics of cyanobacteria and the mechanism of cyanobacterial bloom formation. Gas vesicles and carbohydrates are the common buoyancy regulation mechanisms of cyanobacteria. In addition, new studies have found that large oxygen bubbles produced by unicellular cyanobacteria under light conditions can cause them to rise to the surface. At the same time, cyanobacteria usually exist in colonies in the field, and the oxygen produced in the light filled intercellular space within the colonies is another important factor to affect the buoyancy of the colonies, Meanwhile, a microenvironment was formed in the colonies. The physicochemical properties of the microenvironment within the colonies varied rapidly with changes in external environmental conditions. The microenvironment inside and outside the colonies influenced each other and determined the oxygen concentration inside the colonies, which then influenced the buoyancy of the colonies. Understanding the influence of the buoyancy regulation mechanism of cyanobacteria on the formation of cyanobacterial blooms and the internal microenvironment on the buoyancy of the colonies is of great importance for further understanding the growth characteristics of cyanobacteria and analysing the formation mechanism of cyanobacterial blooms at the microscopic level. This paper summarises the main buoyancy regulation mechanisms of cyanobacterial colonies in the field for a better understanding of the mechanism of cyanobacterial blooms.