The cell carbohydrate content of cyanobacteria can alter buoyancy, and the ability to regulate the buoyancy is one of the most important mechanisms of cyanobacterial blooms. The net accumulation of carbohydrate in cell is affected by photosynthesis, respiration, synthesis of proteins, and other metabolisms, which are connected to the growth. The aim of this work is to seek the relationship between growth rate and intracellular carbohydrate content. The cell carbohydrate content in Microcystis aeruginosa cultures with different growth characteristics was investigated, and the relationship between growth rate and accumulated carbohydrate in cyanobacterial cells was analyzed. The result showed that the specific growth rate was inversely proportional to cell carbohydrate content. The growth rate was relatively high when the cell carbohydrate content was low. It can be indicated that high growth occurs when cells are buoyant, which favors blooms.