Abstract: In the research, the functional superparamagnetic nanoparticles were developed ( shorted as Fe3O4@CS- Na) through the method of ultrasonic- assisted chemical coprecipitating. Analytic data from transmission electron microscope (TEM) suggested that the diameter of Fe3O4@CS-Na was about 10¹5nm.Furthermore, the Fe3O4@CS-Na nanoparticles was used as a magnetic carrier for the adsorption of lysozyme from the aqueous solution. Due to the small diameter, the adsorption equilibrium of lysozyme onto the nanoparticles reached very quickly within 30min. The adsorption equilibrium of lysozyme onto the Fe3O4@CSNa fitted well with the Langmuir model. The nanoparticles were stable when subjected to six repeated adsorption-elution cycles. In conclusion, the application of Fe3O4@CS-Na might find much potential in lysozyme separation and purification.