Since 2001,the Environmental Conservation Program(ECP) has been launched in the Heihe River Basin,aiming at reallocating water resources and implementing ecological restoration measures to balance socio-economic development and ecological system maintenance.In this paper,we divided the historical period in the Heihe River Basin into two periods(i.e.before and after the ECP),and quantified the contributions of climate change and anthropogenic activities to runoff variations based on the Budyko coupled water-energy balance equations.Results indicate:runoff at the Langxinshan station presents a decreasing trend with -0.14mm/a before the ECP and an increasing trend with +0.37mm/a after the ECP.Before the ECP,the decrease in runoff at the Langxinshan station is mainly due to anthropogenic activities in the middle basin,the contribution of which are -0.26mm/a;whereas climate change causes the runoff to increase,the contribution of which is only +0.12mm/a.After the ECP,the increase in runoff at the Langxinshan station is mainly due to climate change,the contribution of which is +0.29mm/a;whereas the impacts of anthropogenic activities on runoff are from negative to positive,the contribution of which are +0.08mm/a.The annual average runoff at the Langxinshan station after the ECP increases by 1.97mm in comparison with that before the ECP.Climate change contributes +1.39mm for the increase(of which the contribution of precipitation is +2.20mm and that of potential evapotranspiration is -0.81mm);whereas anthropogenic activities contribute +0.58mm for the increase,indicating that the ECP has been playing a positive role.