The invention discloses molding sand used for a special casting mould surface. The molding sand is prepared from the following raw materials in parts by weight: 300-330 parts of zircon sand, 55-65 parts of fused magnesite, 12-18 parts of aluminum-magnesium spinel, 20-25 parts of kyanite, 3-5 parts of tributyl citrate, 3-4 parts of copper oxide, 10-15 parts of wood fibers, 2-4 parts of carboxymethyl cellulose, 12-20 parts of graphite powder, 6-9 parts of sodium metasilicate and an appropriate amount of water. According to the molding sand disclosed by the invention, the zircon sand is selected as a main molding material aiming at the characteristics of high casting strength requirements and good fire resistance degree; the quality of the casting mould surface can be obviously improved by the added fused magnesite, aluminum-magnesium spinel and kyanite through processes of roasting, grinding, dispersing and the like; meanwhile, the carboxymethyl cellulose, the graphite powder and the sodium metasilicate are added, so that mobility of the molding sand is increased, mould charging capacity is improved, fire resistance performance is ensured, and molding sand fineness is strengthened. Besides, the molding sand disclosed by the invention is suitable for casting a product with a fine process, high in yield and precise in dimension.