The present invention is a system for harvesting algae in continuous fermentation. There is a harvester including a main moving belt, a plurality of rollers, and a motor for driving the main moving belt. There is a reactor tank and a vacuum extractor for applying a vacuum over a width of the main moving belt to extract biomass and to dry the main moving belt. The main moving belt has one end in the reactor tanks and another end extended into the vacuum extractor. The algae contained in the reactor tank is collected for further processing, including oil extraction. With algae harvested in the large-scale manner of the present invention, a more efficient oil extraction method can be used because the concentration, temperature, and pressure can be more easily controlled.