Experiment using 100 field moist soil samples showed that potassium release was found in 96% of the samples after air-dried treatment. For the soils with higher release capacity of K, the correlation between uptake amount of K by wheat and rice and K content in moist soils was more significant than that between the uptake amount of K and K content in air-dried soils. It indicates that moist soil is suitable to be nerd for analysis of K in soils with higher release capacity of K and lowar content of slowly availsble K. Only a little K could be released from the moist soil containing abundant K after submergence and incubation. Through alternation of wetting and drying,more 8 could be released from the soils richer in hydromicas or montmorillonite. However, it was difficult to increase available K in the soils with lower release capacity of K through submergence or alternation of wetting and drying. The amount of released K increased with the increase of drying temperature. When the tempemature was lower than 200℃, the released K was mainly derived from slowly available K, while the temperature was up to 400℃, the released K was mostly derived from mineral K. Most of the released K under the temperature above 60℃, was not derived from adsorbed K. The increase of exchangeable K in moist soil after air drying was closely related to the saturation degree of K in the soil. More K could be released from the sails containing such minerals as hydromica. The fixation range of fertilizer K applied into moist soils was 18%-56%. Generally the fixation of K increased significantly with the increase of drying temperature. The fixation capacity of K was dependent on sail properties.