Abstract:The Cupressaceae Bartling consists of about 115- 125(-150) species belonging to 20(22) genera, which widely distribute in the Northern and the Southern Hemispheres. To-date, the karyotypes of 55 representative species in 14 genera of the family have been made. The relative locations of the species‘ karyotype coordinate points, which are constructed from the measured data of chromosome by using the mean arm ratio and the chromosome ratio of the longest to the shortest of the complements as the abscissa (Y-axis) and the ordinate (X-axis) respectively, reflect their evolutionary trend and relationships (Fig.1 ). The coordinate points of the two hemispheres can be separated from each other by a straight line with only a few exceptions. Based on the karyotype data, a new cytotaxonomic system of Cupressaceae 6ncluding temporarily the genera having karyotypic data) is proposed as follows.