NOVELTY - Synthesis of tilmicosin involves adding tylosin fermentation filter liquor and pre-fermentation broth to silicon polyacetylene-treated frame filter, cleaning with ceramic membrane system, concentrating, discharging permeate and concentrate, adjusting pH value, collecting butyl phase, adding 3,5-dimethyl-piperidine and formic acid, reacting, sampling by high performance liquid chromatography analysis, insulating, analyzing samples, adding medicinal activated carbon, decolorizing, filtering with titanium rod filter, hydrolyzing, slowly adding hydrochloric acid, adjusting pH value, slowly warming, analyzing samples, and reacting.    USE - Method for synthesizing tilmicosin (claimed).    ADVANTAGE - The method is environment-friendly, and suitable for large-scale industrial production, and has high yield, and reduces use of organic solvent and production cost. The product has high purity.    DETAILED DESCRIPTION - A tilmicosin is synthesized by adding pre-fermentation broth to 1% silicon polyacetylene-treated frame filter, cleaning with ceramic membrane system, concentrating by nanofiltration, opening material feed valve, flowing liquid material into concentrate tank through valve, pump, and flow meter, adjusting frequency control electromagnetic flow meters to meet set value, pump frequency and pressure regulator, discharging permeate and concentrate, filtering, concentrating, cleaning inlet valve and pump, replenishing water, preventing air from entering system, drying, concentrating, adjusting pH value to 10.5-11.0, collecting butyl phase, washing, drying, adding 3,5-dimethyl-piperidine and formic acid, stirring, reacting, stirring for 2 hours, sampling by high performance liquid chromatography analysis, cooling to 22-26 degrees C, insulating, sampling, analyzing samples to obtain tylosin content of greater than or equal to 1.5%, adding medicinal activated carbon, decolorizing for 40 minutes, filtering with titanium rod filter, hydrolyzing, stirring, slowly adding 15% hydrochloric acid to adjust pH value, maintaining temperature at 20-25 degrees C, adjusting pH value, slowly warming to 60 degrees C, incubating for 4 hours, analyzing samples, and reacting at 60 degrees C.