Abstract: Karyotypes of three local populations of Allium fasciculatum Rendle were analyzed. The karyotype of the population from Dagze of Xizang was 2n=2x＝20=4m+10sm +4T+2t(2SAT), the one from Xiangcheng of Sichuan was 2n=2x＝20＝10sm+6t(2SAT)+4T, and the one from Lixian of Siehuan was 2n＝2x=20＝6m+10sm+2t (2SAT)+2T. Although there were differences in karyotypes among the three populations, they were very similar in morphological characters, except that plants in the Dagze population were lower. The karyotype of the Lixian population is considered to be a primitive one that has evolved into the more asymmetrical karyotypes of the Dagze population and Xiangcheng population by structural aberration. In the genus Allium, only four species, A. fasciculaturn, A. decipiens Fisch., A. kujukense Vved. and A. cheloturm Wendelbo. have so far been found to have the basic chromosome number of x＝10. According to karyotype characters and the distribution pattern of these four species, the basic number x = 10 may have different origins. At least that of A. fasciculatum is different from that of the other three species and might have originated the latest. A. fasciculatum was similar to A. hookeri Thwaites (the latter has x＝11) in karyotypical and morphological characters. Therefore, they are considered to have originated from a common extinct ancestor that had the basic number of x = 10.ey words Allium；A．fasciculatum Rendle；Karyotype differentiation