Abstract: In order to obtain the deformation and strength parameters and other related parameters of unsaturated intact loess in the loess tableland regions of Gansu Province, the triaxial consolidation drained shear tests are performed on the unsaturated intact loess with various initial suctions and net confining pressures. The deformation characteristics, critical state, strength parameters and suction variation characteristics of unsaturated intact loess are studied under the constant water content. The results show that the shear failure of intact loess belongs to plastic failure and exhibits significant shear contraction phenomenon. Under different initial suctions, the critical states of deviatoric stress and body strain are all linear. The strength envelope of undisturbed loess in p-q plane can be normalized to a straight line, and it can be expressed approximately with the critical state line of saturated soils. The shear strength of unsaturated loess is influenced by matrix suction, and the cohesion of unsaturated loess increases with the increase of the suction. The effective internal friction angle is less affected by the suction, which can be approximated as a constant. The strength parameters of unsaturated undisturbed loess in the loess tableland regions of Gansu Province are obtained. Besides, the parameter K has a great influence on the suction and there is a linear relationship between the parameter K and the suction.