Abstract: There is a potential threat to long-period operation in the sector of embankment upon the slope. Process of infiltration can not only disturbe field of temperature, but creates infiltrating force. The force can reduce the stability of embankment on the slope in the southern limit region of the permafrost zone. Stability of embankment of the Qinghai-Tibet railway on slope is analyzed in the event of rainstorm where the result of infiltrated calculation is used. Consequently, the stability continuously decreases. The minimal value appears after about two days of rainfall.