Method for preparing injection-grade oxytetracycline

The invention discloses a method for preparing an injection-grade oxytetracycline, which mainly comprises the following steps: directly dissolving the active pharmaceutical ingredient oral-grade oxytetracycline, and decolorizing with activated carbon to remove impurities; and converting oxytetracycline salt into oxytetracycline alkali without adding any flocculant, carrying out vacuum drying and the like. The technical process disclosed by the invention is simple and convenient to operate, and achieves the standard for injection-grade oxytetracycline; and the yield is enhanced by more than 5% as compared with the traditional technique.