The aim of this work was to develop an alginate-casein composite microsphere as a bioaetive vehicle for oral administration of nutrients by a simple extrusion dripping method. Riboflavin was selected as a model drug, and the microencapsulation efficiency was raised to 97.94% after optimizing the preparation conditions by response surface methodology. In vitro release studies showed that riboflavin was released completely from alginate-casein microspheres in simulated intestinal fluids. Meanwhile, the morphology, structure and interaction between alginate and casein were characterized by scanning electron microscopy （SEM） and Fourier transform infrared （FTIR） spectra.
