Marine　microorganisms　have　been　proposed　as　a　new　kind　of　protein　source.　Efforts　are　needed　in　order　to　transform　the　protein-rich　biological　wastes　left　after　lipid　extraction　into　value-added　bio-products.　Thus,　the　utilization　of　protein　recovered　from　defatted　Schizochytrium　sp.　by-products　presents　an　opportunity.　A　specific　peptide　Tyr-Leu　(YL)　with　calcium-binding　capacity　was　purified　from　defatted　Schizochytrium　sp.　protein　hydrolysates　through　gel　filtration　chromatography　and　RP-HPLC.　The　calcium-binding　activity　of　YL　reached　126.34　+/-　3.40　mu　g/mg.　The　calcium-binding　mechanism　was　investigated　through　ultraviolet,　fluorescence　and　infrared　spectroscopy.　The　results　showed　that　calcium　ions　could　form　dative　bonds　with　carboxyl　oxygen　atoms　and　amino　nitrogen　atoms　as　well　as　the　nitrogen　and　oxygen　atoms　of　amide　bonds.　YL-Ca　exhibited　excellent　thermal　stability　and　solubility,　which　was　beneficial　for　its　absorption　and　transport　in　the　basic　intestinal　tract　of　the　human　body.　Moreover,　the　cellular　uptake　of　calcium　in　Caco-2　cells　showed　that　YL-Ca　could　enhance　calcium　uptake　efficiency　and　protect　calcium　ions　against　precipitation　caused　by　dietary　inhibitors　such　as　tannic　acid,　oxalate,　phytate　and　metal　ions.　The　findings　indicate　that　the　by-product　of　Schizochytrium　sp.　is　a　promising　source　for　making　peptide-calcium　bio-products　as　algae-based　functional　supplements　for　human　beings.