Abstract: Taking 11 strains screened from 165 cabbages（2n = 2x = 20）as the materials，which contain the 2n gamete，and the buds of them were treated with different concentration of the colchicines to induce the production of higher 2n gamete；The sexual polyploidization were carried out by the female parent of the tetraploid male-sterile line and it，and the tetraploid was obtained by screening the F1 progeny. Results show that：The optimum condition for the induction of 2n gamete was injecting 5–10 μL 0.20% colchicine into the bud at 3 mm length for once time. The induction frequency of 2n male gamete was 20.20%，which was 3.63 times of the control，untreated with colchicin processing of the plants. In the 80 F1 hybrid progeny，14 plants were identified as tetraploid plants（2n = 4x = 40）by chromosome counting technology. The ratio was about 17.5%. Compared with the diploid plant，the production of tetraploid by sexual polyploidization showed gigantism in plant，stomata，and flowering organs，while the density of stomata and fecundity were decreased remarkably.

Key words: Brassica campestris ssp. chinensis Makino, colchicines, 2n gamete, sexual polyploidi- zation, tetraploid