Abstract: Using plant source of fatty acid methyl esters as solvent，green surfactants as emulsifier， environment-friendly β-Cypermethrin EW was prepared. Optimal formualtion was obtained by screening of the solvent and surfactant：β-Cypermethrin 5%，laurate methyl 14.5%，APG-AEO3（6∶4 by mass）5%，deionized water was added to 100%. On this base，the wetting ability of the optimized EW was studied through dynamic surface tension and dynamic contact angle measurements using ordinary and commercial β-Cypermethrin EWs as comparison samples. The results showed that the surface tension and the contact angle of the 500-fold dilured sample of the optimized EW decayed more quickly with time increasing campared with ordinary and commercial β-Cypermethrin EWs. The excellent wetting and spreading properties made the EW easily adhered and spreaded on the leaf surface to maximize biological activity.