Soil organic carbon and total nitrogen concentrations,soil texture,and carbon and nitrogen densities in different stages of desertification process(Potential,Light,Medium,Severe,and Most severe desertification) in Horqin sandy land were studied.The results showed that along the spectrum from potential desertification to most severe desertification,soil organic carbon and nitrogen concentrations decreased by 91.6% and 85.8%,respectively,to a depth of 100 cm,versus decreases of 95.7% for the fine particle size fractions(<0.1 mm).Carbon density decreased from 4 877.9 to 481.8(C) g/m~2 during deserification process,whereas nitrogen density decreased from 518.0 to 89.4(N) g/m~2.Regression analysis revealed significant positive relationships amongthe soil carbon concentration,soil nitrogen concentration,and soil fine particle size fractions(<0.1 mm) content for all five stages.Soil carbon and nitrogen were lost more rapidly during the initial stages of desertification than the later stages.The soil C/N ratio decreased from 9.385 to 5.541 along the desertification developing.There was a greater proportional decline in soil carbon than in nitrogen.