In order to research the mechanical characteristics of intact Middle Pleistocene Epoch loess,triaxial shear tests and isotonic compression test of intact Middle Pleistocene Epoch loess were conducted by improved SJ-1A triaxial shear equipment.According to test results,it can be found that the intact Middle Pleistocene Epoch loess has the properties of shear dilataney and shear shrinkage.With the increase of confining pressure,stress-strain curve develops from softening to hardening.The failure mode of intact Middle Pleistocene Epoch loess is shear failure with the rupture angle between 55° and 61°.And it is better to determine the yield stress (py,qy) of the intact loess under different confining pressures by using the εv-q/p curve.Along with the increase of confining pressure,yield deviatoric stress qy and yield spherical stress py present logarithmic relationship.Besides,the strength parameters,elastic modulus K and G of intact loess,are obtained,which are benefit for loess projects design.