As a widely used and expensive herbal medicine, Panax ginseng has many adulterants in the commercial market. PCR-restriction fragment length polymorphism (PCR-RFLP) and amplification refractory mutation system (ARMS) based on 5S rDNA sequence analysis were applied to identify two common adulterants of P. ginseng. The sizes of 5S rRNA gene non-transcribed spacers (NTS) sequences in P. ginseng and its adulterants were determined, ranging from 143 to 424 bp. The PCR product of P. ginseng only could be digested among the tested specimens because of its specific SpeI restriction site found in the 5S rDNA sequence. In addition, P. ginseng was successfully identified from compound medicinal preparations and from the Single-Taste medicines. These results suggest that the methods are able to authenticate P. ginseng.