The invention discloses a medicine for treating rhinitis, as well as a preparation method and application thereof. The medicine is prepared from the following raw materials in parts by weight: 3-7 parts of cleome seeds, 10-20 parts of poplar flowers, 15-25 parts of diospyros morrisiana and 13-21 parts of phyllanthus ruinaria. The preparation method comprises the following steps: grinding and screening cleome seeds and diospyros morrisiana, soaking a saline solution, performing microwave treatment to prepare a mixed liquid A; grinding and screening poplar flowers, adding deionized water for ultrasonic treatment, and stirring to prepare a poplar flower solution; grinding and screening phyllanthus ruinaria, adding deionized water, heating and stirring to obtain a phyllanthus ruinaria solution; mixing the mixed liquid A, the poplar flower solution and the phyllanthus ruinaria solution, performing ultrasonic treatment, centrifugally separating, removing precipitate, and stirring until the mixture is dry. The medicine has the advantages of small dosage, convenience in taking, wide application range, exact treatment effect, no relapse after healing, no drug dependence and no side effect, and is safe and reliable; and the preparation process is simple, has low cost, and is suitable for industrial production.