Based on experiments and comparing analysis, the physicochemical characteristics of crust above the loess soil is discussed mainly, and some results were obtained. Crust formation is a physical process that the framework formed by fine sand and coarse silt is filled by small grain(< 0.01mm). The content of humus is nearly same as that of soil while the content of CaCO₃ is slightly lower. Crust hardness has negative relation with the water content of earlier stage, and has positive relation with bulk density and thickness. The relat ion of bulk density and thickness is more complicated.