The invention relates to an optional stem and leaf herbicide for a
paddy field and a preparation method thereof, and in particular relates to a bispyribac-
sodium dispersible oil suspended agent and a preparation method thereof. The bispyribac-
sodium dispersible oil suspended agent comprises the following components in percentage by
mass: 10-20 percent of bispyribac-
sodium, 2-30 percent of emulsifier, 0.2-5 percent of a
wetting agent, 0.3-5 percent of a dispersing agent, 0.5-4 percent of a
thickening agent, 0.01-5 percent of a defoaming agent, 0.1-1.5 percent of a pH regulating agent, and the balance of an oil-based
solvent. The preparation method comprises the following steps: adding the emulsifier, the
wetting agent, the dispersing agent, the
thickening agent, the defoaming agent and the pH regulating agent into the oil-based
solvent, mixing and stirring; adding the bispyribac-sodium
drug under stirring of a high-speed shearing
machine at a rotating speed of 1,500-10,000 revolution / minute, and shearing for 10-40 minutes; and
grinding the mixture by a sand mill until the grain
diameter D90 is less than 8 mu m to obtain the bispyribac-sodium dispersible oil suspended agent.