The start-up and suspending of the solid particles in the action of the hydraulic agitation is theoretically analyzed in this paper, and the critical velocity calculation model about the start-up and suspending of the solid particles is also summarized. The rule of the hydraulic agitation and the effect of some factors are researched with given fluid rating and pressure by the mean of model experimentation. The conclusion is also analyzed and explained with the theories of the hydromechanics. Chinese Hannong-650 sprayers is representative in China, but there are some problems on agitation. This kind of the sprayer is ameliorated based on theories and experiments, and resigned the position of the hydraulic agitator in tank on sprayer, s＝7cm，h＝8cm，θ＝50°, distance of agitation nozzles is 50 mm, minimal agitation flow rate is Q0=41.37 L/min. So the uniformity of the agitation is improved to international standard, efficacy of agitation is above 91%.