We identified Aspergillus .sp IS254 from licorice, which can convert glycyrrhizic acid (GL) into single glucuronic acid glycyrrhetinic acid (GAMA). Based on the study, the optimized fermentation medium contained 1.19g GL, 2g NaNO3, 0.7g MgSO4, 1g K2HPO4 and 0.01g FeSO4 in 1L fermentation liquid. In addition, the best pH was 5.5, and the inoculum amount was 10 ml. Cultures were incubated at 28℃ for 6 days. In the end, the transformation rate could reach 35.72%.