Aimed at homogeneity principle of water mix with pesticide in the jetmixing apparatus, a mathematical model for solving the interior concentration field was established, CFD software called Fluent was used to calculate the field. Timeaverage mass fraction of pesticide was obtained. Intensity of segregation was introduced to quantitative evaluate the mix degree of water and pesticide. The water was mixed with pesticide uniformly when intensity of segregation was 0.05. As the increasing of area ratio, the shortest mixing distance decreased with the area ratio m∈［2.56,4.00］. The mixing performance of jet-apparatus with m=3.06 was better than the jet-mixing apparatus with m=2.56 and m=4.00. The diffusive mixing zone appeared after the maximum turbulent intensity average rate decreased by 14.96%. And the coordinate interval was X∈［(-13.85m+111.37)mm，116.5mm］.Therefor,when measure the concentration in jetmixing apparatus by experiment, it should according the coordinate interval and area ratio to choose the appreciate concentration measurement point.