The invention discloses a preparation method of sutacillin, and belongs to the technical field of biological medicines. The preparation method of the sutacillin comprises the following steps: (1) weighing sutacillin tosilate, adding the sutacillin tosilate into an
organic solvent for dissolving, cooling and stirring, dropwise adding an alkali solution, stirring until a
system is dissolved, separating liquid, taking an organic phase, adding a dehydrating agent for
drying, and filtering to obtain filtrate; and (2) adding a
seed crystal into the filtrate obtained in the step (1), carrying out primary vacuum concentration, cooling, stirring and crystallizing, carrying out secondary vacuum concentration, adding an
organic solvent when the filtrate is concentrated until no obvious fraction exists, and carrying out gradient cooling and
crystal growing, filtering, pumping and
vacuum drying to obtain the sutacillin. The sultacillin
bulk drug prepared by the method is high in yield, high in purity and stable in
chemical property. Moreover, according to the preparation method of the sutacillin, generation of
related impurities possibly caused in the crushing process is avoided, the production cost is saved, the production efficiency is high, the particle size of the sutacillin
raw material medicine can be effectively controlled, and the
dissolution effect is good when the sutacillin
raw material medicine is prepared into an oral preparation.