To characterize jet mixture profiles for inline injection of pesticides, twophase flow fields in conventional mixing chambers were investigated under various test conditions. The twophase flow was formed with water mixed with either a watersoluble liquid or a fatsoluble liquid (silicon oil). Test results illustrated that there were limitations for the conventional mixers to obtain uniform mixtures with the fatsoluble pesticide. To overcome these limitations, a new mixing device based on the swirling jet mechanism was conceived and developed to improve the mixture uniformity of water and the fatsoluble pesticide. The swirling jet mixer consisted of a spiral curved shrink tube, a diffuser and a guide vane to accelerate the twophase flow spiral movement and blend the two liquids. A computational fluid dynamics program (Fluent) was used to simulate the flow field inside the swirling jet mixer to optimize its design. The mixture uniformity was evaluated by introducing the uniformity index γa, representing that the two liquids were blended homogenously as γa was 1. Simulated results showed that the γa was 0.9989 across the entire cross sections inside the mixer, confirming uniform mixture profiles with the new mixer design. 〖JP3〗Therefore, the new swirling jet mixer would solve the nonuniform mixture problem associated with conventional mixers and could significantly improve the inline injection technology to reduce pesticide waste.