Cross-linked microcapsules entrapping ascorbic acid magnesium salt as a core material are prepared by in-situ copolymerization of styrene and divinylbenzene in a (W/O/W) emulsion system, The effects of the preparation conditions of the microcapsules on the capsule morphologies, the entrapment efficiency and release profiles of the core material are investigated, The entrapment efficiency of the core material is improved by lowering the volume fraction of the dispersion phase in the (W/O) emulsion and adding the salt to the outer aqueous phase when tricalcium phosphate is used as the dispersion stabilizer. Both the entrapment efficiency of the core material and the internal morphologies of the microcapsules affect the release profiles of the core material.