Abstract: The diploid pokeweed（Phytolancca American L.）was induced by 0.2% colchicine solution. Three treatments（24h、48h and 72h） were done and morphologic and cytologic comparison between obtained variant plant and CK were studied. The results showed that the treatment of 48h was the best. Comparing with CK, leaf thickness was increased by 43.75%, length and width of stomata by 52.94% and 73.01% respectively, number of chloroplasts by 20.91%, diameter of flower by 22.96%, diameter of pollen by 22.47%, diameter of fruit by 23.66%. Leaf index was declined by 37.95%. By chromosome observation of pollen mother cells, it showed that the chromosome number of microspore in the variant plants is n=2x=36, but the chromosome number of microspore in CK is n=x=18, so it was tested that the variant plants were autotetraploid.