A method for preparing a biopesticide preparation for preventing and controlling Solenopsis invicta comprising: a: preparing an agent containing pathogenic microorganisms for preventing and controlling Solenopsis invicta, the agent comprises Beauveria bassiana and sodium chloride, with a Beauveria bassiana spores to sodium chloride ratio of (1-8)×20 billion spores: 4.0-7.5 g; b: placing the agent into a solid container, and adding a corresponding amount of solution in a liquid container; inserting the solid container into the liquid container, wherein a retaining ring is stuck at the opening of the liquid container, a rubber gasket is pressed against the retaining ring, and a lid covers the rubber gasket and the retaining ring and is fixed to the opening of the liquid container.