The invention discloses a veterinary drug for treating respiratory tract infection of poultry and a preparation method thereof. The veterinary drug is prepared mainly from the following materials by weight part: 30-120 parts of radix stemonae, 10-120 parts of scutellaria baicalensis, 30-210 parts of giant knot weed, 10-60 parts of indigo naturalis, 10-60 parts of artificial bezoar, 10-40 parts ofborneol, 10-90 parts of realgar, 10-60 parts of liquorice, 30-120 parts of platycodon root, 90-210 parts of cyrtomium fortunei, 30-120 parts of blackberry lily, 10-210 parts of dried toad, 150-420 parts of radix isatidis and 1-10 parts of bromhexine hydrochloride. The veterinary drug is prepared by grinding, screening and evenly mixing the materials, and grinding the materials by a superfine pulverizing technology into submicron powder and packing. The veterinary drug is mainly used for treating respiratory diseases of poultry caused by the bacterial viruses such as infectious bronchitis of chicken, infectious laryngotracheitis, newcastle disease and influenza. The invention has the advantages of rapid drug effect, favorable effect and little remaining charge, has simple preparation methodand is easy for promotion and application.