The high-speed imaging technology was applied to study the mixing uniformity of the mixer. The polystyrene was chosen as the tracing particle to follow the flow of the liquid pesticide. The mixing images were acquired with the changed work conditions of the pump. Then, the centroid coordinates of particles were obtained. At last, the results of the mixing performance were analyzed. It was found that the different work conditions of the pump and the distribution of the particles had different effects on the mixing performance. The results showed that when the particle centroid distribution of the tracing particle was closer to the normal distribution, the mixing performance was better. When the pump worked in a low speed, the mixing uniformity was getting better with the increasing of pump pressure. When the working pressure of the pump was constant, the mixing uniformity increased gradually as the speed of the pump increased.