Objective To explore the value of the molecular probe USPIO-PEG-sLeX on nasopharyngeal carcinoma xenograft in nude mice.Methods The USPIO nanoparticles was synthesized by physical deposition method,and which was modified by PEG to synthesize USPIO-PEG-sLeX .The nude mice of nasopharyngeal carcinoma xenograft were divided into experimental and control groups.USPIO-PEG-sLeX and USPIO-PEG were injected into nude mice of experimental and control groups by caudal vein,respectively.MR T2 mapping imaging was scanned before and after the injection,and analyzed the changes of T2 values between experimental and control groups. Results USPIO-PEG-sLeX had a good representation.The non-enhanced T2 values between control and experimental group had no statistical significance (P >0.05).However,T2 values of the mice in two groups before and after injections were statistically significant (P <0.05);and T2 values of experimental group were much lower than that of the control group after the injection,additionally,the difference of enhanced rate between the two groups was statistically significant (P <0.05).Conclusion USPIO-PEG-sLeX magnetic nanoparticles is potential to be a targeted contrast agent to ELAM-1 expression of nasopharyngeal carcinoma,and can be valuable in non-invasive dynamic monitoring the expression of ELAM-1.