Abstract: The uniaxial compressive strength is one of the main mechanical properties of soil,and it is also an important criterion for the foundation design in cold region engineering of 58 samples.Lanzhou loess are prepared with different water contents and salt contents for exposure to a maximum of 10 closed-system freeze-thaw cycles in order to study the influence of cyclic freeze-thaw on physical and mechanical properties of salty soil,especially the uniaxial compressive strength at room temperature.The experiments indicate the way of the failure of the salty soil is brittle fracture obviously from the relationship of stress-strain,though the salty soil with freeze-thaw cycles has no yielding phase,and it has plastic failure after it reaches the ultimate stress.And the strength of the salty soil is strengthened and weakened due to the mix of the sodium sulfate;and to get a new dynamic equilibrium of the loess with sodium sulfate,the required freeze-thaw cycles are 6.