The dynamics of imidazolium ion and its influence on proton conductivity were investigated for imidazolium hydrogen succinate crystal using solid-state H-2 and C-13 NMR. A 180 degrees flip and libration (rotational vibration) of the imidazolium ion were observed from H-2 NMR broad line spectra, quadrupole Carr-Purcell-Meiboom-Gill (QCPMG) spectra and high-resolution C-13 NMR spectra. From a comparison of the rates of these motions and proton transfer, the libration of imidazolium ion is important for the proton conductive process.