Lithium ion conducting La1 3-xLi3xTaO3 (x=0.06, LLT) with an A-site deficient perovskite structure was synthesized via sol-gel method. A homogeneous LLT precursor solution was prepared from La((OC3H7)-C-i)(3), LiOC2H5, and Ta(OC2H5)(5) in 2-methoxyethanol. Gel powders which were obtained by hydrolyzing the precursor solution, crystallized to a metastable cubic perovskite phase at 820 degreesC, whereas a tetragonal phase with the ordered arrangement of A-site cations and vacancies formed when the gel powders were fired at 1200 degreesC. La-Li-Ta-O gel films on SiO2 glass substrates crystallized to the cubic LLT at 800 degreesC. The tetragonal LLT films with the (0 0 1) orientation were successfully prepared on SrTiO3 (100) substrates at 1000 degreesC. The LLT films prepared on both substrates were smooth and had neither cracks nor voids. The lithium ion conductivity of the LLT films synthesized on the SiO2 glass substrates became higher as the firing temperature increased up to 1000 degreesC, probably because of their enhanced crystallinity. On the contrary, the (0 0 1) oriented LLT films synthesized on the SrTiO3 (100) substrates at 1000 degreesC revealed much higher conductivity than those synthesized on the SiO2 glass substrates; this would be ascribed to the anisotropic conduction in the ordered tetragonal phase or the reaction at the interface between the films and the SiO2 glass substrates.