The degradation mechanism and time-dependent failure mechanism in high steep rock slope are investigated in the cold region. Experiments of triaxial compression and triaxial creep are carried out on the quartz sandstone samples experienced different freezing-thawing cycles. The difference of mechanic property and failure model under the action of short-term stress and long-term stress are focused on. Experimental results show that the freezing-thawing action made little effect on mechanical properties of sandstone under short-term stress. The conventional mechanical parameters and acoustic emission (AE) phenomenon just decreased slightly with the increase of freezing-thawing cycles. However, the freezing-thawing action made great effect on mechanical properties of sandstone under long-term stress. With the increase of the freezing-thawing cycles, the creep mechanical parameters changed with increasing freezing-thawing cycles obviously. This is because that the freezing-thawing result in the fatigue damage of the crack wall and the particle in the crack wall can deform sufficiently, causing the obvious creep properties. The long-term reduction factor, which can predict current situation accurately, is proposed for symbolizing the ability of resisting to long-term load of sandstone. In addition, the failure patterns of rock under the action of short-term and long-term stress after different freezing-thawing cycles both are shear failure. But the broken way of rock under the action of long-term stress developed gradually from single oblique cutting surface to X-shape conjugate shear surface with increasing freezing-thawing cycles and the broken degree is more serious. The result is of great significance for the whole life cycle assessment of major projects in highland and cold region.