Abstract: In order to promote the industrial production of emamectin benzoate microcapsule suspension, 1% emamectin benzoate microcapsule suspensions was prepared via in-situ polymerization process, using urea-formaldehyde resin as the wall material. The influence of solvent selection, emulsifier and its dosage, stirring rate, acidification time, curing temperature and the amount of substance ratio of prepolymer formaldehyde and urea on the performance of microcapsules was studied. Emamectin benzoate microcapsule with preferable encapsulation rate (83.8%) and average particle size (2.3 μm) was formed under the optimal conditions, when the compound emulsifier (m (603^# ) : m (500^# )=5 : 1) dosage was 2.4% mass fraction, the stirring rate was 300 r/min, the acidification time was 120 min, the curing temperature was 70 ℃, the amount of substance ratio of prepolymer formaldehyde and urea was 3 : 1, and the mass fraction was 20%. HPLC analysis showed that emamectin benzoate microcapsule had a favorable slow release performance, which can achieve 17-day sustained-release under test conditions. At the same time, bioassay experiments targeting the 3rd instar larvae of Plutella xylostella showed that the microcapsule suspension had good sustained-release bioactivity. And the duration was longer than the control agent.