Mg-Al spinel has been synthesized by using alkali corrosion slag from aluminum profile factory, decomposed magnesite and used MgO-C brick as the main raw materials. The influence of decomposed magnesite and used MgO-C brick powder after calcinations process on crystalline constitution and micro-morphology of synthesized Mg-Al spinel specimens are discussed. The synthesized specimens are characterized by XRD and SEM, and the crystallinity of crystalline phase is calculated by X' Pert plus software. The experimental result shows that the crystalline phase periclase increases with the increasing of magnesia generated by used MgO-C brick powder. The crystallinity of crystalline phase is maximum when the addition of used MgO-C brick powder after calcined at 800°C is 30wt%. Magnesia generated by sintering decomposed magnesite powder at 700°C showed more effective than magnesia generated by used MgO-C brick powder to react with impurity in alkaline corrosion slag.