Spirulina (Arthrospira platensis)， a paragon of commercial applications of alga， has been widely cultivated as an economic product around the world. As one of the luminous energy transporters in a structure called phycobilisomes in cyanobacteria and microalgae， phycocyanin has been gaining attention as a natural blue colorant and a physiological active compound. Phycocyanin showed several health benefits such as anti-inflammatory， anti-tumor， anti-oxidant， and immunomodulatory， which have been fully tested， hence it is very promising for the application of phycocyanin in the area of drug delivery. However， purified phycocyanin is prone to precipitating and/or dissociating when dissolved in the water， and demonstrates high sensitivity to environmental stresses such as temperature， pH， light， and ion. In the field of colorant protection， researchers devoted themselves to the stability improvement of phycocyanin on the nanoscale such as nanoparticles and nanoemulsions， to keep its robustness in harsh conditions in food processings and storages. In the field of physiological activity maintenance， researchers hammered at bioaccessibility improvement of phycocyanin by adding oligosaccharides and/or preservatives， or modifying its molecular structure via physical methods and/or chemical methods， as well as forming various nanocarriers for phycocyanin delivery. In addition， phycocyanin， a fluorescent protein， has been employed as a shell material of nanoparticles， applied to the mediation of metal nanoparticles， utilized in the formation of fluorescent probes， and so on. In this paper， applications of phycocyanin were summarized， and prospects for its development were presented as well.