Abstract: To explore the effect of potassium in tobacco leaf and forms of potassium in different layers of soil and to solve issue of low potassium content in tobacco in central Henan, an experiment was carried out in Xiangcheng, Xuchang of Henan province in 2013.Two levels of potassium fertilizer were used, and the tobacco were irrigated for three times, between accumulation of potassium in tobacco leaf and content of different forms of potassium in different depth of soil were analyzed using gray correlation analysis, The results showed that with the three irrigation and use of low levels of potassium fertilizer, correlation coefficient was 0.7059, indicating that tobacco potassium content was most closely correlated with slowly available potassium in the 0-20 cm soil.With the irrigation three times and use of high levels of potassium fertilizer, correlation coefficient was 0.7350, indicating that tobacco potassium content was most closely correlated with rapidly available potassium in the 40-60 cm soil and leaf potassium content was 1.88%, and it is also the best quality of tobacco leaves.With the decrease in potassium fertilizer rate and irrigation, their correlation with potassium content in tobacco and in different layers of soil was more significant.Frequent wet-dry alteration would help release slowly available potassium, thus increasing the level of rapidly available potassium.When fertilizer ratio was at N:P₂O₅:K₂O = 1:1:4.5, and irrigated for 3 times, increasing potassium fertilizer rate and frequency of irrigation was an good means to address the problem of low potassium content of tobacco in the late growth.