In order to explore the origin and evolution of tuber mustard（Brassica juncea var. tumida Tsen et Lee），we cloned and sequenced the Chs gene sequences of tuber mustard and its close relative species．As illustrated in the phylogenetic tree，the sequences from all Brassica taxa were separated into three well supported clades and nine sub-clades．Splits tree analysis indicated that there existed not only tree evolution，but also reticulate evolution among tuber mustard and its related plants．Median-joining（MJ）network analysis showed that B. rapa and B. nigra were the parental donors of A genome and B genome in allotetraploid B. juncea tumida，respectively．Tuber mustard，as a variety of B. juncea，was closely related to B. juncea var. utilis，indicating that B. juncea tumida might originate from B. juncea var. utilis．In addition，the single copy gene Chs could be efficiently applied to evaluate the phylogenetic relationships of tuber mustard its and related plants.