Abstract: Based on studing external morphological characters of Solanum nigrum L., S. nigrum L. var. flavovirens S. Z. Liou et W. Q. Wang and S. nigrum L. var. pauciflorum Liou in china have been studied. The difference in colour of ripe fruit and leaf shape of S. nigrum L. var. flavovirens S. Z. Liou et W. Q. Wang and S. nigrum L. has been found, which is in colour of ripe fruit and trichome shape and size of organ of S. nigrum L. var. pauciflorum Liou and S. nigrum L.. Through cluster analysis, S. nigrum L. var. pauciflorum Liou is one class. S. nigrum L. and S. nigrum L. var. flavovirens S. Z. Liou et W. Q. Wang are another class. S. nigrum L. var. pauciflorum Liou shows primitive character, which has been considered to be an independent species, S. pauciflorum (Liou) H. Y. Zhang. S. nigrum L. and S. nigrum L. var. flavovirens S. Z. Liou et W. Q. Wang are different polyploid species which evoluted from S.nigrum L. var. pauciflorum Liou.

Key words: Solanum nigrum, Variation, Comparative morphological, Cluster analysis