Preparation method of tetracycline hydrochloride

The invention relates to a preparation method of tetracycline hydrochloride, which comprises the following steps: dissolving urea double salt generated by reaction of tetracycline and urea in an acidic 95% ethanol solution according to a ratio of 1: (5-8) at 17-19 DEG C under a stirring condition, filtering the 95% ethanol solution, heating the filtrate to crystallize, controlling the heating speed to 20-40 minutes, keeping the temperature for 30-90 minutes after the temperature is raised to 43-52 DEG C, and filtering to obtain the tetracycline hydrochloride. And then starting a refrigerant for cooling, when the temperature is reduced to 30-22 DEG C, carrying out solid-liquid separation on the crystalline liquid, and drying to obtain a tetracycline hydrochloride finished product. According to the method, 95% ethanol is adopted to replace n-butyl alcohol to crystallize tetracycline hydrochloride, and a low-temperature dissolving and slow heating mode is adopted, so that the product yield and content are improv