Although iron oxide(Fe3O4)nanoparticles have broad application prospects as magnetic resonance imaging(MRI)contrast agent,their biocompatibility and biotoxicity still need to be improved.In this study,we prepared Fe3O4@Angelica sinensis polysaccharide nanoparticles(Fe3O4@ASP NPs)with a 9 nm Fe3O4 core and ASP as the coating material.The Fe3O4@ASP NPs are superparamag-netic,can be taken up by liver and spleen macrophages in the circulatory system in vivo,and are a good-biocompatibility and low-toxicity transverse relaxation time(T2)and T2-star(T2*)magnetic resonance imaging(MRI)contrast agent for the liver.The cytotoxicity assessment using HeLa cells and the pathological tests in mice validate that Fe3O4@ASP NPs have low toxicity and good biocompatibility in vivo,which can be attributed to the ASP as a natural polysaccharide with good biocompatibility and its function of protecting the liver.Fe3O4@ASP NPs are a potential new MRI contrast agent with high signal intensity in vivo.