Abstract: Using ethanolic solution of iodine as catalyst, the free magnesium oxide (f-MgO) in steel slags was extracted with glycol as solvent and determined by EDTA titration. Optimum values of the amount of iodine-ethanol solution and the ratio of K-B indicator were studied. It was shown that the end point of titration was found to have an obvious color change when the ratio of acid chrome blue K to naphthol green B in the solution was 1∶1.4 and the mass ratio of iodine to MgO was 7.5∶1. Test for recovery was made by addition of pure MgO to steel slag, giving values of average recovery of 96.5% and RSD (n=5) of 1.3%.