Abstract: Chlorella is a unicellular microalga that could grow and accumulate biomass through photosynthesis using sunlight and carbon dioxide. It is widely used to produce biofuels and other high-value products in fields like aquaculture, food, energy, and the environment. With the development of genetic engineering technology, research and applications of Chlorella at the molecular level have received increasing attention, making specific genetic modification possible. In this paper, we summarized and discussed the application of Chlorella in genetic engineering and protein production from four perspectives:transformation system, transformation methods, factors affecting transformation and expression of exogenous proteins. The aim of this review was to provide theoretical support and references for high-value products production of Chlorella.