Dextran-based microspheres have become growingly attractive in the fields of surface coating, printing, pharmaceutical and other industrial applications. In an effort to prepare the dextran-based microspheres, methacryloyl(MA) groups were introduced into dextran(Dex-MA) molecules as a crosslinking functional group via the transesterification reaction. The resulting Dex-MA was characterized by use of 1H NMR, 13C NMR, FT-IR, and GPC. Degree of substitution(DS) of the MA groups in the glucopyranose ring of a dextran molecule was calculated from peak intensities of 1H NMR spectrum and compared well with the calculated value. The aqueous two-phase polymer system(ATPS) emulsion, which consists of Dex-MA, PEG, and water, was used for preparation of the microspheres. To this purpose, the phase diagrams of several Dex-MA/PEG/water systems at 25 ℃ were constructed. Microparticles with a volume mean diameter from 7.7 to 38 μm could be prepared in a reproducible way. The DS could be used to tailor the size, the initial water content, and the swelling property of the resulting microspheres. In addition, the swelling properties of the microspheres were measured by means of the blue-Dex solution method and the gravimetric method.