The invention discloses a formula and a preparation method of an external preparation for allergic rhinitis, wherein the components of the external preparation mainly comprise cordyceps sinensis essential oil, cornu cervi pantotrichum essential oil, ginseng essential oil, peppermint essential oil, menthol, fructus xanthii oil, flos magnoliae liliflorae oil and menthol, and the cordyceps sinensis essential oil, the cornu cervi pantotrichum essential oil, the ginseng essential oil, the peppermint essential oil, the fructus xanthii oil and the flos magnoliae liliflorae oil are prepared from cordyceps sinensis, cornu cervi pantotrichum, ginseng, peppermint, fructus xanthii and flos magnoliae liliflorae through a supercritical CO2 extraction and steam distillation combined method. The preparation process of the preparation mainly comprises carrying out supercritical extraction on the Chinese herbs to obtain various oil-like products, extracting mixed volatile oil through a distillation method, uniformly mixing with peppermint, and sub-packaging. According to the present invention, the preparation product can effectively treat allergic rhinitis, can provide a certain treatment effect for acute and chronic rhinitis, dry rhinitis, nasal congestion, nose running, sneezing, headache, hyposmia, nasal obstruction, common cold, belly pain, diarrhea, vomiting, mosquito biting, dyspepsia, scorch by soup and fire, toothache, headache, carsickness, sea sickness and the like, and further has effects of summer-heat removing, refreshing, wind expelling, disinfection, inflammation eliminating, and the like.