The rhizomes and herbal medicines originating from Acorus gramineus, A. calamus, A. tatarinowii, and A. gramineus var. pusilus, show significant similarity, and the correct identification of species is very difficult. Random Amplified Polymorphic DNA (RAPD) and Sequence Characterized Amplified Region (SCAR) were used to develop a reliable method for identification of these four species. Several distinct SCAR markers were developed from species-specific RAPD amplicons for each species. Furthermore, a useful molecular marker was established for multiplex-PCR, in order to the four species could be distinguished concurrently. These markers allow efficient and rapid identification of closely-related Acorus species and will be useful for standardization of herbal medicines.