Abstract: The effect of agroforestry on environmental quality was studied by isotope trace technique and the field experimentation,the results showed:(1)The capacity of fixing CO2 of the agroforestry was 1.6～2.1 times as much as that of the single agricultural system because of the existence of tree.On an average,the content of CO2 in the agroforestry was 55～95 mL·m-3 lower than that in the single agricultural system.(2)Poplar,willow,wheat and maize could absorb N2O by an certain degree.(3)There were no significant difference about the CH4 content between inside and outside the agroforestry system,i.e,there was no obvious CH4 gas exchange between crops and atmosphere.(4)In the sandy soil area,agroforestry could reduce the transporting dust capacity effectively,and reduce the falling dust capacity by 20%～60%.Wind-protection effect,intensity of turbulent current exchange and soil moisture were the main factors that determined the falling dust capacity.