Taking the Huan County of Gansu province located in the south part of agriculture pasture ecotone as research area,temporal variation of driving factors of land desertification for the last 65 years was analyzed using principal component analysis based on 16 statistical data of social and economic factors from 1949 to 2013. Result show that: (1) The process of desertification in Huan county for last 65 years could be divided into three time phases,including 1949 ~ 1979,1980 ~ 1999 and 2000 ~ 2013 according to the contribution rate of human activity factors to land desertification 46.21%, 36.25% and 44.79%,respectively. Natural factors contribution rate from 1949 to 1979 was 26.45%,it was 11.32% higher than that of 1980 ~ 2000 and 4.87% higher than that of 2000 ~ 2013. Furthermore,Comprehensive factors contribution rate from 1980 to 1999 was 30.77%,it was 21.41% and 12.18% higher than that from 1949 to 1979 and from 2000 to 2013,respectively. (2) The influence of climate change on desertification was relatively small,but the human activity was the much more active factor to the desertification and reverses desertification. It mainly incarnated on the changes of the dramatically - increased population and agricultural population,unreasonable landuse caused by excessive reclamation as well as pastures degradation induced by overgraze; Moreover,the influence of natural factors mainly incarnated on the changes of temperatures rising,lower rainfall,increased evaporation and decreased sir relative humidity which may led to soil drought and development of soil dried layer,inhibition of plant growth and vegetation coverage as well as the ability to resist erosion of the soil. However,factors for accelerating soil erosion were the strong and consistent wind and storm rainfall. (3) The implementation of land combined contract system in 1980 and the policy of returning farmland to forest (grass) in 2000 have little impact on the influence of human factors; as for the three phases,contribution rate from natural factors was declined,but contribution rate from comprehensive factors was increased.