In this paper, magnetic Fe3O4@LMWCS14 nanoparticles were synthesized through biocompatible low molecular weight chitosan with 14 degree of polymerization (LMWCS14) coating on the surface of Fe3O4 nanoparticles. The structure and morphology were characterized by FFIR, TGA, XRD, SEM, TEM and DLS. FTIR confirmed the presence of LMWCS14 in Fe3O4@LMWCS14 nanoparticles. TGA results showed that the content of LMWCS14 in the composites was about 46.3%. XRD suggested that the crystalline structure of Fe3O4 nanoparticles was unchanged in the composites. TEM and DLS results demonstrated that Fe3O4@LMWCS14 nanoparticles were spherical morphology and better dispersed with the average size of about 17.2 nm after modification with LMWCS14 layer. Besides, magnetic resonance imaging (MRI) efficiency in vitro was evaluated. The transverse relaxivity (r(2)) of Fe3O4@LMWCS14 nanoparticles was up to 278 mM(-1) s(-1) and the composites presented a desired T-2-weighted imaging contrast effect at lower dose, indicating that Fe3O4@LMWCS14 nanoparticles was promising to be an effective T-2 contrast agent. (C) 2016 Elsevier B.V. All rights reserved.