The invention provides a preprocessing method for gasification ammonia-cyanide-phenol-contained circulating water. Particularly, slag scraping and oil removal are performed on gasification circulating water through advective oil separation pool, then, a coagulant, magnetic powder, an oil emulsion separated out by a flocculating agent, colloid and suspended solid sediments are added, the sediments can remove oil pollutants in water, and the magnetic powder can be recycled; coagulation, flocculation and air flotation are performed at the upper portion of a settling pond, the coagulant is added so that destabilization of the oil emulsion, the colloid and the suspended solid can be achieved, small alumen ustum is generated, the flocculating agent is added into sewage obtained after coagulation, the alumen ustum is gathered into firmer alumen ustum, flocculation water and circulating water with rich microbubbles are mixed and then enter a floatation tank, and uniform oil sludge cakes are formed on the surface of the floatation tank; processed water flows into a suction well and is recycled to an inlet of the floatation tank, and the preprocessing process of the gasification circulating water is completed. The gasification circulating water is preprocessed, the content of oil in water is decreased, and the loading coagulation oil remover and floatation technology are adopted to remove floating oil and dispersed oil in the water.