Abstract: The seedlings of six varieties of Chinese cabbage with different coldness were treated at low temperature for 0, 8, 15, 22, 29, 36, 43 d respectively, the time of bud emerging of them were investigated and compared, the results showed that the requirement of low temperature treatment days for vernalization is dependended on the coldness of variety, the weaker of coldness, the shorter of low temperature treatment is needed, the requirement range is from 8 days to more than 29 days respectively. As the low temperature treatment days is increased, the floral bud is emerging earlier; the duration for all plant emerging bud is shorted. It was found that the light during low temperature treatment is needed for vernalization, the plant do not produce floral buds even treated for 29 d under dark condition. When the different coldness varieties with different seedling age were treated at 4—5 ℃ for 25 days, it was found that the sensitivity to low temperature for vernalization is 4—5 leaves seedling>2—3 leaves seedling>7—8 leaves seedling, such as the time of bud emerging is earliest in 4-5 leaves seedling，latest in 7—8 leaves seedling for weaker coldness varieties, and the days for all plant producing bud is shortest in 4—5 leaves seedling, and longest in 7-8 leaves seedling for all various coldness varieties.

Key words: Chinese cabbage, seedling, vernalization, temperature, light, floral bud