Abstract: In civil engineering,the deterministic system is usually used for soil classification,but it can not provide the quantitative information for the spatial interpolation.The fuzzy k-means is often used to quantify the soil classification but no comparison with other systems had been given.In this paper FKM was compared with USCS to validate its abilities of classification which have been improved with a formula of fuzzy similarity measure.Based on the probabilistic distribution,the confident interval of distribution of soil groups could be estimated.The process of establishment of 3D soil map was illustrated in a practical case.