Even though the degradation of ginsenosides has been thoroughly studied in animals and in vitro using acids, enzymes, and intestinal bacteria, a new degradation method is established for obtaining the ginsenosides Rg(3), Rh(2) and their aglycon 20(S)-protopanaxadiol. This method is based on the microwave irradiation degradation of the major ginsenosides from the Panax quinquefolium L. coupled with foam floatation. The results indicated that ginsenosides Rg(3), Rh(2) and aglycon are not naturally present in Panax quinquefolium L., but are the products obtained simultaneously in the microwave irradiation degradation process. The yield of Rg(3) is 7.69 mg/g and 250 times as high as that obtained from red ginseng, and the transformation rate of total ginsenosides to aglycon is 78.11%. It is important to stress that a new degradation medium, N,N-dimethylformamide, was discovered and, when the medium was used, the transformation rate of total ginsenosides to aglycon was 20.20%. The proposed method is simple, efficient, time saving and a noteworthy improvement on the traditional degradation methods such as acidic hydrolysis, alkaline degradation, enzymatic conversion or microbial degradation.