The title ternary complex La(C5O3H3)3 x C12H8N2 x H2O was synthesized by reaction of lanthanum nitrate with alpha-furoic acid (C5O3H4) and 1,10-phenanthroline (C12H8N2) as ligand in the alcohol solvent. The composition of the complex was determined by element analysis. Its structure and properties were characterized by IR, 1H NMR, UV and TG-DTA. IR, 1H NMR, UV spectra showed that the ligand alpha-furoic acid coordinate to the center ion La (III) with the deprotonized form, and 1, 10-10phenanthroline with the bidentate form using its two N atoms. The TG-DTA analysis exhibited that the complex is stable in the range of room temperature and undergo the disassociation of water and oxygenized decomposition of the organic ligands in order with the rising of temperature, and the final oxide obtained is La2O3. The quantitative analysis of TG-DTA was coincided with the structural composition of the title complex.