The effect of Fe2O3 on the sintering property of MgO-CaO refractory was studied by XRD analysis and SEM analysis of sectioned specimens. As the content of ferric oxide increases, the specimen has higher density, lower porosity and the cold crush strength increases. In contrast the density and porosity of the fired specimens change slightly when the content is up to 6%. From XRD analysis, ferric oxide do not exist owing to that ferric oxide reacted with calcium oxide producing calcium ferrite; From SEM analysis, when the content of ferric oxide is 6%, calcium ferrite distributes uniformly between the main crystal phase and the matrix and the overall structure is homogeneous and dense. The result shows the nonuniform distribution of calcium ferrite as the content of ferric oxide is relatively low, while as the content of ferric oxide is high the excess amount of calcium ferrite existed in the sintered specimens will generate superfluous liquid phase to reduce the fire resistance of materials.