[Objective] To study how shear strength change with the variation of water content and dry density in undisturbed and disturbed loess paleosol in order to provide the basis for selecting the parameters in design and construction of slope project

tunneling and underground structure engineering in loess area[Methods] Direct shear tests were conducted on undisturbed and disturbed paleosol with different water contents and dry densities.[Results] Under the same dry density

cohesion of both undisturbed and disturbed paleosol decreased with the increase of water content. While under the same moisture content

the cohesion of undisturbed paleosol was greater than the cohesion of disturbed paleosol. The internal friction angle increased with the increase of the water content.[Conclusion] The shear strength index of loess paleosol increases with the decrease of moisture content. An exponential relationship exists between cohesion and water content

and a quadratic parabola relationship exists between internal friction angle and water content.