Abstract: In the present paper the chromosome number and karyotype of Cycas guizhouensis are reported, and they are compared with those of C. panzhihuaensis, C.revoluta、C.rumphii、C. circinalis and C.media. The karyotype formula of C.guizhouensis is K(2n)= 22=2m+4sm+4st + 12T identical to C. panzhihuaensis. Both species distribute in the north of the Tropic of Cancer. The karyotype of C. guizhouensis is more advanced than many other species of the genus Cycas such as C. revaluta, C. revoiuta, C. circinalis and C. media which are known to be K(2n)=22=4m+8st+10T and distribute in the south of the Tropic of Cancer. On the other hand. C.guizhouensis is more primitive than C. panzhihuaensis.