The invention discloses a Swainsonia salsula Taub. acaricide and its preparation method. Swainsonia salsula Taub. Plants undergo a certain processing process to prepare a wettable pulvis, missible oil, an emulsion in water, a microemulsion and the like of the Swainsonia salsula Taub. acaricide. Tests prove that the acaricide of the invention has the advantages of substantial drug effect, high selectivity, low toxicity, low residual, difficult generation of pest mites' resistances to the acaricide, simple preparation technology, and low cost, accords with present pesticide development trends, and is suitable for the popularization and the application.