The invention discloses a slag pot in steel mills produced by heatproof cast iron. The slag pot comprises a pot body, the pot body is the heatproof cast iron, and is produced by the following components by weight percentage: 3.4-3.6% of C, 1.8-2.2% of Si, 0.60-0.80% of Mn, 2.0-2.2% of Cr, 0.35-0.60% of Mo, less than 0.03% of P, 0.08-0.10% of S, 0.02-0.03% of Re, and the balance of iron. According to the invention, the slag pot in steel mills has the advantages of good thermal conductivity, strong high-temperature resistance, strong oxidation resistance, good heat fatigue resistance, and obviously-increased service life. The invention also discloses a production method of the slag pot in steel mills produced by the heatproof cast iron.