New reduced tantalates, Li2LaTa2O7 and Li2Ca2Ta3O10, with layered perovskite structure were synthesized by electrochemical or chemical intercalation reaction of lithium from the parent Dion-Jacobson series compounds. The crystal structures of these compounds were determined by the Rietveld analysis of powder X-ray diffraction pattern. The crystal structures of intercalation compounds were analogous to those of the parent compounds. The intercalation of the lithium ion leads to a large contraction along the stacking direction of perovskite layers because of a higher interlayer charge density. These intercalation compounds are the first example of reduced tantalates with layered perovskite structure.