Abstract: The good quality of pesticide application in agricultural production is very important. One of the important indexes for evaluating the application quality is the even distribution of chemicals on targets. And the well mixing spray in the tank before applying is prerequisite.The dynamic factors and the filling level in the tank of sprayers which influence the efficacy of agitation were studied on the tank of a Hannong 650 field sprayer. It was discovered: the efficacy of agitation was improved both by the increase of the flow rate and the working pressure of back flow, and the efficacy of the increasing flow rate seemed better than that of the increasing working pressure. And the more filling of spray in the tank was the more well mixing of spray would be, and vice versa.