Unsaturated loess from Lanzhou City was studied to understand how matrix suction affects its shear strength. The main factors influencing matrix suction changes are the structure, mineral composition, and soluble salt content of the loess. Residual water content and density of the loess samples have an inverse relationship. The presence of montmorillonite and illite layers in the loess, as well as soluble salts, also impact matrix suction changes.