The invention relates to a method for purifying factor B, comprising the steps consisting in:(i) obtaining a blood plasma fraction containing factor B(ii) subjecting the fraction obtained in step (i) to a heparin-like affinity chromatography(iii) subjecting the factor B-enriched fraction obtained in step (ii) to a cation exchange chromatography(iv) subjecting the factor B-enriched fraction obtained in step (iii) to an anion exchange chromatography,(v) eluting the factor B.
