The invention is directed to an improved process for preparing cefsulodin sodium. The process involves: (i) dissolving cefsulodin in a solvent comprising an organic solvent to provide a solution of cefsulodin, (ii) adding about 1 equivalent of a sodium salt of a base to the solution of cefsulodin to provide a solution of cefsulodin sodium, and (iii) separating the cefsulodin sodium from the solution of cefsulodin sodium.