Microalgae　is　one　of　the　most　important　components　in　the　aquatic　ecosystem,　and　they　are　increasingly　used　in　food　and　medicine　production　for　human　consumption　due　to　their　rapid　growth　cycle　and　survival　ability　in　the　harsh　environment.　Now,　the　exploration　of　microalgae　has　been　gradually　deepening,　mainly　focused　on　the　field　of　nutrition,　medicine,　and　cosmetics.　A　great　deal　of　studies　has　shown　that　microalgae　have　a　variety　of　functions　in　regulating　the　body　health　and　preventing　disease,　such　as　nitrogen　fixation,　antitumor,　antivirus,　antioxidation,　anti-inflammatory,　and　antithrombotic.　Furthermore,　microalgae　can　synthesize　various　high-valued　bioactive　substances,　such　as　proteins,　lipids,　polysaccharides,　and　pigments.　In　this　paper,　we　have　briefly　reviewed　the　research　progress　of　main　bioactive　components　in　microalgae,　proteins,　lipids,　polysaccharides,　pigments,　and　other　nutrients　included,　as　well　as　their　present　application　situation.　This　paper　can　provide　the　guidance　for　research　and　development　of　industrial　production　of　microalgae.