Magnetic catalyst was made of magnetic core and surface coating layer and obtained a core-shell complex materials. The magnetic γ-Fe2O3 core has a relatively higher saturation magnetization, coercivity and good thermal stability even at 500°C. In order to prevent magnetic core forming spinel structure and migrating of Fe3+, a layer of silicon dioxide was coated by sol-gel method. During the process iron atoms scattered in –Si-O-Si- network and produced a γ-Fe2O3@SiO2 structure. Finally, the γ-Fe2O3@SiO2 powder was put into the alumina sol and evenly sprayed into a column of oil, after calcination the carrier of alumina layer was prepared.