The invention discloses an internal floating roof tank pipeline sweeping system. The internal floating roof tank pipeline sweeping system comprises an internal floating roof tank, a floating tray, a blowing pipeline, an oil product pipeline, a sweeping pipeline, a metal hose, a sweeping entering tank pipeline, a gas-liquid separation tank and a diffusion pipe, wherein the gas-liquid separation tank is installed and fixed at the tank top of the internal floating roof tank, the blowing pipeline is connected to the oil product pipeline in front of the metal hose, a sweeping pipeline inlet is connected out from the oil product pipeline behind the metal hose, a sweeping pipeline outlet is connected to the tube wall of the gas-liquid separation tank, a sweeping entering tank pipeline inlet is connected out from the bottom of the gas-liquid separation tank, a sweeping entering tank pipeline outlet is connected to the oil product pipeline behind the metal hose, and a diffusion pipe inlet is connected out from the top of the gas-liquid separation tank. By means of the internal floating roof tank pipeline sweeping system, a sweeping gas medium contained in a pipeline blowing oil product canbe effectively separated, and the sweeping gas medium is avoided from entering the internal floating roof tank, so that internal floating roof tank pipeline sweeping safe running is realized; the internal floating roof tank pipeline sweeping system is concise in process method and structural style, good in feasibility and low in investment; and the method is suitable for a newly-built internal floating roof tank pipeline sweeping system and is also suitable for upgrading and reconstruction on an existing internal floating roof tank pipeline sweeping system.