Phycocyanin is a protein pigment complex of the phycobiliprotein family that plays a role in absorbing sunlight for photosynthesis. Phycocyanin is used in the food and beverage industry as a natural "Lina Blue" colorant and which is widely used in candy, snacks and ice cream. Phycocyanin is also used in cosmetics such as lipstick and eyeliner. Spirulina contains very high levels of phycocyanin (15%), and it is easily adapted to cultured conditions in Vietnam. In this study, we carry on a study on the extraction of phycocyanin from spirulina with high efficiency (>
80%) by ultrasonic extraction and developed a method to determine the phycocyanin content in Spirulina algae which was commercially available with repeatability and high repetition (RSD