The molecular mobility of deoxycholic acid (DCA) / ferrocene inclusion compound has been investigated by high resolution solid state C-13 NMR spectroscopy. Compared to the single crystal of ferrocene, the molecular mobility of the ferrocene in the inclusion compound is enhanced because it is included in the large cavity of DCA. It is found that the relaxation time measurement by solid state C-13 NMR can provide powerful evidence to confirm the formation of the inclusion compound.