Objective To investigate the methods of preparing a specific molecular probe for magnetic resonance imaging targeting endothelial cell adhesion molecule-1 (ELAM-1) with ultrasmall superparamagnetic particles of iron oxide(USPIO) chelating sialyl-Lewis X (sLeX), and research its physicochemical properties. Methods Using physical deposition method to synthesis USPIO nanoparticles. By hydrophobic interactions, preferable water-soluble PEG-SPIO was synthesized and the surface -COOH was sufficiently activated,then incubated with sufficient sLeX at room temperature, purified by centrifugal ultrafiltration and washed with deionized water. The magnetic resonance molecular probe USPIO-PEG-sLeX was prepared and characterize it. Results TEM results revealed that the PEG-SPIO had a size of (10±2.6)nm with good dispersibility and suitable size. DLS study showed that before and after coupling,the hydrodynamic mean diameter were (34.06±9.95)nm and (53.35±16.99) nm, respectively. Zeta potential study showed that before and after coupling the potential of PEG conjugated magnetic nanoparticles potential were (11.6±3.96) mV and (-12.6±5.33) mV,respectively. Conclusion The method of chemical conjugation can be successfully prepared MRI molecular probe USPIO-PEGsLeX, which has a well-characterized molecular probe, and it is expected to meet vivo experiments specifically binds to ELAM-1 requirements.