The accumulation,distribution and content changes of glycyrrhizic acid of a medicinal licorice Glycyrrhiza uralensis Fisch.were investigated by means of immunohistochemical localization and HPLC methods.The results showed that:(1)The glycyrrhizic acid distributed mainly in the cell wall of phloem parenchyma cells and ray cells of the roots;(2)The content of glycyrrhizic acid in different tissues of taproot was varied.The highest one was in phloem and then in xylem,while the lowest in the root bark.(3)The content of glycyrrhizic acid tended to increase with the growth years in the roots.It increased quickly in 2years and 3yesars and the content of glycyrrhizic acid is 3.66% in 3yaers,which exceeds the standard of Chinese pharmacopoeia.The results provide a further understanding on the internal mechanism of the quality formation of medicinal licorice and to improve quality of medicine licorice.