Geometry optimization and total energy computation were carried out for TiS2, LiTiS2 and intercalation compound LixTiS2(x=1/4, 1/3, 1/2, 2/3, 3/4)ordered systems using first principles method based on local density approximation to density-functional theory. The computation results for these systems have been compared with other experimental and theoretical results available in the literature. The normalized increments of lattice parameters Δa0 and Δc0 increase monotonicly with the increasing concentration of Li ion. The curves show good agreement with lattice parameters obtained from experiment. The formation energies of ordered systems LixTiS2(x=1/4, 1/3, 1/2, 2/3, 3/4) are all negative, indicating their stability at low temperature. The formation energy of Li1/2TiS2 system with 3a0×a0 ordered structure is the lowest, implying the most stable structure. The results have shows that the local density approximation to density-functional theory can reasonably be applied to TiS2, LiTiS2 and intercalation compound LixTiS2(x=1/4, 1/3, 1/2, 2/3, 3/4)ordered systems.