The invention relates to a preparation method for
flucloxacillin sodium. The method comprises the following steps of: (1) weighing 6-
aminopenicillanic acid, 3-(2-chloro-6-fluorophenyl)-5-methyl
isoxazole-4-
phosgene and
sodium iso-octoate; (2) adding water into 6-
aminopenicillanic acid, cooling in an ice bath, and adding
acetone to obtain a solution A; (3) preparing 3-(2-chloro-6-fluorophenyl)-5-methyl
isoxazole-4-
carbonyl chloride and an
organic solvent into a solution B; (4) adding the solution B into the solution A, and performing an
acylation reaction; (5) after reacting, acidifying, and adding an
organic solvent for extracting; (6) slowly adding a part of organic solution of
sodium iso-octoate into the an extracting solution obtained in the step (5), performing a salt-forming reaction, and growing a
crystal after the
crystal is precipitated out; and (7) after growing the
crystal, continually adding the residual
sodium iso-octoate solution, preserving heat, stirring, leaching, soaking, washing and
drying in vacuum. The method has the advantages of short process
route, high process
operability and capability of effectively increasing product quality and yield.