The invention relates a process for preparing a cross-linked starch-based polymer comprising the following steps: 1) dissolving a starchy material in a suitable solvent to form a starchy material solution； and 2) adding a episulfide of formula (I), wherein R1, R2, R3 and R4 are independently selected from hydrogen and (C1-C3)alkyl in the starchy material solution in order to obtain the disulfide crosslinked starch-based polymer. In another aspect the invention concerns a disulfide-cross-linked starch-based polymer obtainable by the process of the invention, that is characterized by only disulfide bridges.
