The contents of 12 ginsenosides (Rg 1, Re, F 11, Rf, Rg 2, Rh 1, Rb 1, Rc, Rb 2, Rb 3, Rd, Rh 2) in different parts and ages of Panax quinquefolius L. (American ginseng) were quantified by high pressure microwave-assisted extraction (HPMAE) high-performance liquid chromatography coupled with evaporative light scattering detection (HPLC-ELSD). The analytical method was established and analytical performances were evaluated. The chemical marker of American ginseng F 11 was detected, and Rf which is the chemical marker of Asian ginseng was not found. Rare ginsenoside Rh 1, Rg 2 and Rh 2 were also studied in this experiment. The total contents of these 12 ginsenosides in the different parts of 5-year-old American ginseng follow this order: leaf > root-hair > rhizome > root > stem. Therefore, compared with the other parts of American ginseng, the leaf is a better available source of ginsenosides. The contents of ginsenosides in root and leaf also change with age.