Field trial for studying the effect of different potassium levels on corn yield of different potassium fertility soils was carried out. The results showed that in higher rainfall year the yield and K use efficiency on Aeolian sand of low potassium fertility was higher than that on Black soil of middle and high potassium fertility. Application of potassium fertilizer significantly enhanced available K in Black soil after harvest, but available K in Aeolian sand soils did not change. The optimum potassium fertilization in low, middle and high fertility soils was 98.2 kg/hm²,39.5 kg/hm² and 49.5 kg/hm², respectively.