Abstract: Mixers play a critical role in direct injection systems, ensuring the uniformity of the distribution in target areas of pesticide deposition. In order to determine the optimal design of a mixer, computational fluid dynamics (CFD) simulations were run on 4 variations of geometry model. The internal flow fields of the mixers were studied and compared by the CFD software,and the result showed that the design of the pipette in the back of the throat was the best. The result of verification tests with these 4 types of mixers on an in-house-made direct injection test bed well coincides with that of the simulation.