Abstract: Accurate preparation of soil samples with different moisture content is extremely important for determination of soil shear strength.A soil automatic uniform wetting device was designed with the idea of ‘uniform wetting and easy operation’.Soil automatic uniform wetting was achieved through oscillation，spray，airtight container and automatic control.The device could make up defects of traditional soil preparation long time，low operation precision and low water content.It made soil sample preparation more convenient and quick.Application prospect of this soil automatic uniform wetting device was good.