The invention relates to a preparation process of impurities contained in an expectorant drug bromhexine hydrochloride and belongs to the field of pharmaceutical technology and medicinal chemistry. The preparation process comprises the steps of preparation of an impurity C, an impurity D, an impurity E, an impurity F, an impurity G and an impurity H and has the advantages that the purity of the impurities is high, the preparation method is simple, complex separation and purification methods are not needed and the gram-level sample can be prepared at one time, sufficient qualified references can be provided for the quality control of bromhexine hydrochloride, a guarantee is provided for improving the quality of the hydrochloride bromine drug and the primary problems that the references of impurities contained in bromhexine hydrochloride depend on import and the cost is very high are solved.