By investigation of the microstructure of cerium-doped NASICON materials prepared by solid state reaction, we find that variation in the cell parameters a, b and c can affect their activation energy (Ea) of ionic conductance. Furthermore, changes in the grain size and morphology can influence the pre-exponential factor σ0. Analysis of the electrical conductivity of cerium-doped NASICON grains reveals a decrease from that for the undoped grains. These results suggest that when dealing with Ce-doped NASICON system, the grain size and morphology play a more important role in determining the bulk conductivity than the lattice parameters, at least within a temperature range of 225–350°C.