Licorice is the root and rhizome of the legumes. Glycyrrhetinic acid， bioactive ingredient in licorice， has great application value. By preliminary screening and rescreening from ediblestrains， this study selected Aspergillus niger， which hasstrong ability toproduce glycyrrhetinic acid. Based on the research of the Response Surface Method， this research optimized the fermentation conditions for Aspergillus niger （A） transforming glycyrrhetinic acid， the factors include content of licorice， content of concentrated apple juice， content of wheat bran and the fermentation time. The results showed these four factors havegreat effect on transformation of glycyrrhetinic acid， and the optimum fermentation conditions were as following： content of licorice was 9.83%， content of concentrated apple juice was 8.05%， content of wheat bran was 9.76%， the fermentation time was 6.79 days and the expected conversion rate of 18-α-glycyrrhetinic acid was 0.9256， the result of verification experiment matched the predicted value.