Microwave pre-conditioning Soxhlet method had been used for the extraction of glycyrrhizic acid from Licorice root, with distilled water as extractant. The effect of microwave power, irradiation time, pre-conditioning water capacity and extraction time on the yield of extracts (rude glycyrrhizic acid) were respectively studied. Combining with the resistance analysis of objective components diffusing from matrix inside to extractant, the enhancing mass-transfer mechanism of extraction was discussed, with the...