Abstract: The uniaxial compression test results of Q2 loess in various water contents in Xi’an show that the strain-stress relationship of Q2 natural loess is strong strain-soften type,the inflection point of the curve decreases with the increase of water content,and the decreasing degree of structural strength under lower water content is more than that under higher water content.On the basis of these,Weibull statistical distribution method,equivalent strain hypothesis theory and damage threshold value are used to determin the damage constitutive model of loess under uniaxial compression condition.