Abstract: Michelia chapensis Dandy is firstly karyomorphologically studied. Its karyotype can be formulated as 2n=38=28 m+6 sm+4 st (2SAT), belonging to Stebbins’s 2B type. This is a new karyotype report, which, different from the previous confirmation that in Michelia group, the whole karyotypes of genus are of uniform 2A and there is no st chromosome occurred. There might be different karyotypes within Michelia, and M. chapensis is probably a relatively advanced species. We briefly discuss the role of minor chromosomal structural alterations played in evolution of genus or species in Magnoliaceae.