Safety issues affecting traditional lithium-ion batteries with liquid electrolyte can be successfully overcome by application of a solid electrolyte. Among various candidate materials, perovskite-type compounds, typically from Li3xLa2/3-xTiO3 group, are known to exhibit superior Li+ ionic conductivity. However, the ever-increasing requirement for high ionic conductivity necessitates the improvement of its structure and composition. In this work, Sr2+ cations, having ionic radius larger than La3+, are doped at the La-site in order to enlarge the unit lattice parameter and so facilitate the lithium ion migration process. At the same time, Sr doping can increase the lithium ion concentration of Li0.33+xLa0.56-xSrxTiO3 oxides as charge compensation. Both of them favor the increase of lithium ion conductivity. The Sr substitution induces structure transformation from tetragonal to cubic structure. The prepared dense Li0.36La0.53Sr0.03TiO3 (x = 0.03) ceramic electrolyte exhibits a high ionic conductivity of 1.95 x 10(-3) S cm(-1) at 303 K, which is about twice as high as that of the pristine material.