To investigate flow field characteristics of jet mixing under variable working conditions, a jet flow field was analyzed with CFD simulation method and experimental analysis. The results indicated that the proposed numerical model could exactly predict the mixing ratio changed with outlet static pressure. It is showed that the mixing ratio decreased linearly with the increase of outlet static pressure. The static pressure distributions under different conditions demonstrated that the lowest pressure point along path ade located in mixing chamber was ahead of point d, and the static pressure decreased rapidly in nozzle field and rose up slowly in mixing tube. A local vortex appeared closed to jet core zone along path cd, which was affected by jet flow. The nondimensional performance curves presented a decreasing linear relationship between the pressure ratio and mixing ratio. The prediction error between numerical and experimental results was less than 6%; when the outlet static pressure was higher than 0.45MPa, the reflux status appeared in the jet mixing device which lost the function of waterpesticide mixing online.