Abstract: It is about 70 percent of the whole land area on earth that effected by freezethaw action,but it is 98 percent in China.Freeze-thaw action can effect in varying degrees to factors such as soil moisture,density,organic quality and soil machinery composition.Based on field observation and interior experiment,the relation between freeze-thaw action and soil moisture was studied in Northesat black soil region.Results showed that under the freeze-thaw the soil water flow from lower part with height flow to upper part with low flow,and water content of freezing soil increased.The soil moisture removed lessened soil moisture content of non-freezing layer.The soil moisture migration in the process being frozen led to soil swelling deformation,which is the major factor caused freeze-thaw erosion.