Abstract: In order to improve the performance of off-road vehicle and working efficiency of machines used in the field of construction and agriculture，the mechanism of soil adhesion should be understood.The purpose of this study was to find out the relationship between tangential soil adhesion and moisture content using different tool materials and investigate the effect of tangential soil adhesion on mechanical properties of soil shear.In the experiment，three kinds of experimental material：rubber（RUB），steel（SS400）and resin（PEEK）were provided for direct shear test.The experimental results showed that tangential soil adhesion between soil and material increased with the increasing of soil moisture content until reached a maximum value thereafter decreased.Tangential soil adhesion was largest with steel（SS400）followed by rubber（RUB）and resin（PEEK）.It was also shown that external friction angle between three kinds of tool material and test soil first decreased with the increase of moisture content，then tended to increase gradually thereafter showed a decreasing tendency after reaching peak value.The changes of tangential adhesion caused by the difference of soil moisture content directly affected shear stress and external friction angle while shear happened.