Pingtang County is facing severe water shortage and the agricultural water use makes the situation worse; therefore, there is an urgent need to clarify the key factors affecting the utilization of agricultural water resources in this area, to construct high efficiency agricultural production model, and to improve water resources use efficiency. Using the water footprint research model, quantitative estimation of agricultural water use in Pingtang County from 2001 to 2015 was carried out, and the STIRPAT extension model of water footprint variation was constructed considering six factors including population, economy, technology, urbanization, dietary structure and climate and based on the classical IPAT environmental pressure equation.The main driving factors of agricultural water footprint change in Pingtang County was analyzed. The results show that: the water footprint of Pingtang County increased by 42.86% from 6.02×108m3 in 2001 to 8.60×108m3 in 2015. The increasing footprint of green water and blue water was due to the adjustment of agricultural industrial structure, the improvement of planting technology, the extension of new crop varieties. The rapid growth of ash water footprint was mainly due to the heavy use of chemical fertilizers; The driving contribution of the driving factor of agricultural water footprint change in Pingtang County was ranked from large to small as follows: dietary structure > precipitation > population > economy > Technology > urbanization, and every 1% change in the above driving factors will cause the change of the total agricultural water footprint -0.1071%, 0.09393%, 0.0684%, 0.0585%, 0.0581%, and 0.0453%, respectively. Pingtang County belongs to a typical karst peak cluster depression, and surface storage function is very weak, due to the special surface and underground "dual" structural characteristics. The contribution rate of grey water to agricultural water use growth rate is large, due to heavy use of pesticides and fertilizers. However, the economy is underdeveloped, with low living standard, the dietary structure are mainly vegetative food, which saves agricultural water to a certain extent.