The invention relates to a method for preparing pesticides, in particular to a cyhalofop-ethyl aqueous emulsion and a preparation method thereof, belonging to the technical field of pesticide processing. The emulsion in water includes cyhalofop-ethyl emulsifier, solvent, preservative, thickener, antifreeze and water, and the original medicine of cyhalofop-ethyl is mixed with emulsifier and solvent and stirred to form a uniform oil phase; , antifreeze, preservative, etc. are mixed together to form a uniform water phase; slowly pour the oil phase into the water phase, and under high-speed (5000-6000r/min.10min) shear emulsification, a well-dispersed milky white liquid is obtained. The cyhalofop-ester aqueous emulsion has good fluidity before and after storage, does not agglomerate, does not separate water, does not separate oil, has good stability, and its biological activity is equivalent to that of the same dose of emulsifiable concentrate. However, the cost is lower than that of emulsifiable concentrate, and the prospect of popularization and application is broad.