To study the effects of structure on aero-anion concentration at urban forestry,the concentrations of aero-cation and aero-anion were measured on typical urban forestry,in Jilin city.The data were analyzed with variance-comparing statistical methods.The results are as follows:the concentration is significantly affected by structures of urban forestry.The level of aero-anion concentration and air quality grade is highest in multistratal forest that comprises arbor,brush and lawn,while the lowest is on lawn.The rests show that arbors have a dominant effect on the improvement of air quality.