In this paper, a novel purification method utilizing polymorphism to reduce LHB in the final product of LH has been employed. Two polymorphs of lincomycin hydrochloride (LH), polymorph land polymorph II, are prepared, and their purities are determined by HPLC. The content of lincomycin B hydrochloride (LHB) in polymorph I is higher than that in polymorph II, which is due to the uncertainty of the propyl group in the five-membered ring in polymorph I. The crystal form and the purity of the samples as a function of aging time are studied. Three types of products, polymorph I, mixture of polymorph I and polymorph II and polymorph II, are observed and characterized by powder X-ray diffraction (XRD). The XRD results show that polymorph II from different samples contains different amounts of the particular facet of polymorph I. The relationship between the amount of the residual facet of polymorph I containing in polymorph II and the product purity is established. (C) 2012 Elsevier Ltd. All rights reserved.