The invention belongs to the field of energy utilization, and relates to a system and process for microalgae cultivation by means of chemical-looping combustion CO2 and ash. In the chemical-looping combustion process, high-temperature vapor serves as fluidization carrier gas and a gasification agent of fuel, Fe2O3 is taken as an oxygen carrier, and combustion products are mainly H2O and CO2 and are collected separately; a microalgae cultivation device is a surrounding type tubular cultivation container and simulates the natural growth environment, CO2 is introduced into the container to enhance the photosynthesis of microalgae, and then the growth rate of microalgae is increased; alkali metal in ash generated through chemical-looping combustion is used for preparing a microalgae cultivation solution. The chemical-looping combustion process and microalgae cultivation are tightly combined, two-stage reaction of chemical-looping is fully utilized to generate high-concentration CO2 to be used for promoting microalgae cultivation, and ash generated from combustion is utilized to prepare the microalgae cultivation solution; microalgae cultivation rate and quality are improved, cultivation cost is reduced, and comprehensive utilization of a chemical-looping combustion device and chemical-looping combustion products is achieved.