This work has synthesized a binary solid complex using rare earth ion La3+ with the ligand HL (HL = O-chlorophenoxyacetic acid). The chemical formula of the complex was determined to be LaL3 x H2O by elemental analysis. The composition, structure and properties of this type of complex were tentatiovely investigated by the analysis of molar conductivity, IR, UV, TG-DTA and 1H NMR. The center ion in the complex was considered to be chelated by a bidentate ligand HL.