The present invention relates to an improved process for the preparation of the dihydrochloride monohydrate salt of (S)-2-amino-4,5,6,7-tetrahydro-6-(propylamino)benzothiazole (the compound of formula I) comprising reacting the compound of formula II with n-propanal and sodium borohydride using a mixture of methanol and dichloromethane (DCM) as the solvent to obtain the compound of formula I followed by converting the compound of formula I into its mono hydrochloride salt purifying the monohydrochloride salt of the compound of formula I and finally converting the pure monohydrochloride salt of the compound of formula I into the dihydrochloride monohydrate salt.
