Abstract: Balance status of potassium in soil with 22 years long-term fertilization were studied. The results showed that the potassium surplus was 57.72 (kg/hm2) in NK treatment and deficit of 192.97 (kg/hm2) in NPK treatment during the 1978 to 2000 years. The water soluble potassium, non-specifically absorptive potassium, specifically absorptive potassium and mineral potassium increased by 5.49, 1.13, 2.47 and 1.11 times with NK reatment, respectively. The potassium forms percentage in soil of total K were 19.18% and 20.01% in NPK and NK treatments and the available potassium and slow-release potassium in 0—20cm soil layer of NK and NPK treatments was higher than that in 20—100cm soil layer. The X-ray diffraction diagrams indicated that the clay mineral composition of soil had significant change with and without application of potassium, the peak value of montmorillonite was higher in NPK treatment and vermiculite was higher in NP treatment.