Based on the long - term field experiment of K application on meadow soil, the effect of K fertilizer apphcation on the content and proportion of K was discussed. The result showed that long - term K application could increase the content and proportion of water - soluble K, non - specially adsorbed K, specially adsorbed K, non - exchangeable K in the plough layer, and decrease the proportion of mineral K in the same time. Along with the layer going to deeper, the content and proportion of water- soluble K, non - specially adsorbed K, specially adsorbed K, non - exchangeable K in most treatments decreased, and the effect was more distinct in the treatments of K application, but mineral K and total K behaved the opposite result. K fertilizer application could increase corn grain yield remarkably.