The structure of Na0.8Ti1.2Ga4.8O10 was determined by means of single-crystal X-ray diffraction at 173 and 123 K and reinvestigated at 299 K. The host structure containing one-dimensional tunnels was retained over the temperatures examined, while significant changes were observed in the probability density distribution of Na+ ions in the tunnel. The refinement based on the local structure model with the deviated Na+ ion neighboring the vacancy gave a similar result to that from the conventional model, but with reduced standard uncertainties of the structural parameters for the Na+ ions. The potential barrier for the Na+ ion hopping between adjacent cavities was estimated to be ca 30-40 meV from the joint probability density function of deviated Na+ ions.