Dendrobium catenatum (Dendrobium officinale) is a valuable genuine herb. The source of this species is difficult to be identified by traditional methods including morphology, spectroscopy, and chromatography. We used the restriction site-associated DNA sequencing (RAD-seq) approach to perform the high-throughput sequencing of 24 D. catenatum provenances. In this study, 371.18 Gb clean data were obtained, and 655,057 high-quality SNPs were selected after their filtration. We used phylogenetic tree, genetic structure, and principal component analyses to examine the genetic diversities and genetic relationships of the 109 accessions. We found that D. catenatum could be divided into two groups, and each group was closely related to the distribution of the sampling sites. At the population level, the average nucleotide diversity (π) of the D. catenatum population mutation parameters was 0.1584 and the expected heterozygosity (HE) was 0.1575. The GXLPTP07 accessions showed the highest genetic diversity in terms of the private allele number, observed heterozygosity, and nucleotide diversity. The Mantel test showed a significant positive correlation between the genetic and geographic distances among the overall distribution. A genetic information database of D. catenatum was established, which confirmed that RAD-seq technology has the potential to be applied in the identification of medicinal Dendrobium of different origins.