The present invention relates to a fuel supplying and cleaning system. The present invention is to provide a fuel supplying and cleaning system enabling a pump or an engine to be consistently used by preventing a dirty oil tank from flowing backwards. According to an embodiment of the present invention, the fuel supplying and cleaning system includes: a fuel supply line connected from a fuel settling tank to the engine; a purifier installed in the fuel supply line and filtering contaminants of a fuel supplied from the fuel settling tank; the duty oil tank connected to a discharge line from which the contaminants of the purifier are discharged so that the contaminants filtered by the purifier are discharged and stored; and a blocking valve installed in the discharge line and preventing backflow by blocking the discharge line when the dirty oil tank is filled at a predetermined rate. According to the present invention, the fuel supplying and cleaning system stores sludge filtered by the purifier in the dirty oil tank by opening and closing the discharge line installed from the purifier to the dirty oil tank and prevents the sludge or seawater from flowing backwards to the purifier by closing the discharge line when the dirty oil tank is filled with the sludge or the seawater at the predetermined rate so that the pump or the engine can be operated.
