Abstract: Twenty field experiments of K effect on corn were conducted in the upland red earths in Zhejiang Province. The quantity and intensity relationships of soil K were measured. Results showed that K supplying intensity (AR0), K supplying capacity (-△K0) and K supplying buttering capacity (PBC) ranged from 0.0004499 - 0.006579, 0.3153~ 4.057 and 442.2-941.2 with an average of 0. 002001(molL-1)0.5, 1. 578cmol kg-1. and 683.3 emol kg-1(molL-1)-0.5, respectively. Available K, HNO3 soluble K and slowly available K of soil; relative grain yield, relative total dry matter yield and K uptake of corn in NP plots were used as reference to check the practical applicability of AR0,-△K0 and PBC. The correlation analysis showed that the AR0 and -△K0 were very significantly correlated(p=0.01) with available K, HNO3 soluble K, relative grain yield, relative total dry matter yield and K uptake(NP plot) of corn, significantly correlated (p=0.05) with the slowly available K. PBC were very significantly correlated (p-0.01) with the relative grain yield and relative total dry matter yield of corn, and significantly correlated with soil available K. So, AR0 and -△K0 were the excellent indexes to evaluate soil K supplying powr and the PBC, in a certain degree, could characterize soil K fertility. Also, we found that multiple regression analyses between the reference standards and paraments of AR0,-△K0 and PBC were better than the simple correlation, suggesting a intergrated test of AR0, -△K0 and PBC is necessary to estimate supplying power and availability to plant of soil K.