Abstract:The experiment was conducted to investigate the effects of different types and levels of potassium fertilizer on plant growth, cell protective enzymes and endogenous hormones in flowering Chinese cabbage. Both of two types of potassium fertilizer (KCl, K2SO4) included 5 K2O levels respectively and in total of 9 treatments. The K2O levels was as follows: 0, 3, 6, 9 and 12 kg.(666.7m2)-1. The results showed that both KCl and K2SO4 fertilizer could increase the activities of POD and CAT, and the contents of IAA and GA3, but decreased MDA content, and thus increased the yield of flowering Chinese cabbage. With the increasing of potassium levels from 0 to 6 kg.( 666.7m2 )-1, the contents of IAA and GA3, the activities of POD and CAT and flower stalk yield increased significantly, however, when the potassium levels increased for further, the contents of IAA and GA3 decreased quickly, and POD activities and flower stalk yield kept stable. At the same potassium levels, two types of potassium fertilizer had no effect on plant growth, flower stalk yield and GA3 contents of leaves. At 0～6 kg.(666.7m2)-1 of potassium fertilizer, the POD activities in leaves fertilized by KCl were higher than those fertilized by K2SO4, but at levels of 9～12 6kg.(666.7m2)-1, K2SO4 fertilizer exerted higher promotion on POD activity. CAT activities in leaves fertilized by 6kg.(666.7m2)-1 of KCl and MDA contents in leaves fertilized by 3 kg.(666.7m2)-1 of KCl were lower than those fertilized by same levels of K2SO4. In contrary, treatment with 6kg.(666.7m2)-1 and 12kg.(666.7m2)-1 of KCl exerted higher promotion on IAA contents than K2SO4 fertilizer. At other fertilizer levels, two types of potassium fertilizer had no effects on CAT activity, MDA and IAA contents. In concluded, although two potassium types exerted different influence on the reactive oxygen species metabolic system and endogenous hormones in plants, they had no effects on the plant growth and flower stalk yield of flowering Chinese cabbage at the same levels of potassium fertilizer. Thus, in the field production, KCl fertilizer can be used to save the cost instead of K2SO4 fertilizer, and the effect of 6 kg.(666.7m2)-1 of KCl fertilizer showed the best.