Submicron-size Fe 3 O 4 @silica core/shell microspheres were prepared by sol–gel method. Through coating inert silica shell and adjusting the thickness, the dispersibility of magnetic microspheres in water was greatly improved. The resultant Fe 3 O 4 @silica microspheres with controllable saturation magnetization between 34.3emu/g and 47.3emu/g were superparamagnetic. All as-prepared magnetic composite microspheres possessed fleetly magnetic responsivity. The PAA-modified Fe 3 O 4 @silica microspheres were used for selective adsorption and separation of lysozyme, and the experimental results showed that the maximum binding capacity is about 127mg/g. After surface modification of Fe 3 O 4 @silica with polyacrylic acid (PAA) flexible chains, the binding capacity of Fe 3 O 4 @silica-g-PAA microspheres for lysozyme were 22 times as much as that of pure Fe 3 O 4 @silica microspheres at the same pH condition.