Abstract: Wintergreen oil 200 g/kg capsule suspension(CS) was prepared using aphicidal wintergreen oil as core material and urea-formaldehyde as wall materials,and the preparation process was then optimized.In-situ polymerization was used to prepare the microcapsule.Experiments were performed to produce controlled-release microcapsules of wintergreen oil using a single factorial design.The independent variables were the weight ratio of core/shell material,agitation speed,pH,temperature and dispersant.The microcapsules were prepared with optimum properties under the following conditions:weight ratio of core/shell material at 3:2,3% mixture of SMA and tween 80 (1:1) as dispersant,agitation speed at 800 r/min,adjusting pH value to 2.0 within 120-150 min,and reaction 1 h at 60-70 ℃.The wintergreen oil 200 g/kg capsule suspension was applied to control Macrosiphoniella sanborni (Gillette) in the field at 300 g a.i/hm2,and the control efficacy was still higher than 90% after 11 days,indicating that 20% wintergreen oil capsule suspension is of long effective duration.