Abstract:Amentotaxus argotaenia (Hance) Pilger is valuable and imminent danger plant and be-longs tio the prior protective plant of third class in our county. It is dioecious. Through the chromosomal analysis at the cell of root tip, it is shown as below: the chromosome number in both the female and male plants is found to be 2n = 40. Among them both third to twentieth paris of chromosome are metacentric chromosomes, the third to twentieth paris of chromosome are telochromosomes. The karyootypic formula is 2n=40=4m+36T. Besides there is a little differ-ence of the second pair of chromosome in both the female plant and male plant. The relative length and arm ratio of the other pairs of chromosome all are more approximate. It may not be differentiae in the sex chromosomes.