The invention discloses a gold nanorod immunoprobe applied to various mediums, and a preparation method and application thereof. The gold nanorod immunoprobe is a product obtained by performing the preparation of gold nano seeds, the growth and concentration of a gold nanorod, antibody modification and sealing. The immunoprobe is subjected to specific recognition in various mediums, such as buffer solution, serum, blood plasma or urine, saliva and the like, and is finally qualitatively and quantitatively analyzed by reading the offset of longitudinal plasma absorption peaks of the gold nanorod. When used for detecting corresponding antigens, the immunoprobe has the advantages of simple operation, high detection sensitivity, high specificity, fewer required instruments and devices, and the like. Moreover, as nano composites are well adapted to external mediums by the special modification mode of the immunoprobe, the immunoprobe also has an expanded application range and is possibly popularized to clinical application.