Electron paramagnetic resonance-site directed spin labeling(EPR-SDSL)technology is nowadays an interested technique for its specific usage in the analysis of conformational changing properties relating to molecular interaction.LSECtin can negatively regulate activated T cell in the immune tolerance in liver.The interaction between LSECtin and CD44 is the molecular basis of the binding between LSECtin and activated T cell.In this work,to explore the molecular mechanism of the interaction between LSECtin and CD44,EPR-SDSL technology was used to detect conformational mobility characteristics of different sites on CRD which is the main functional domains of hLSECtin.