Two new organic-inorganic hybrid Keggin-type polyoxometalates containing lanth-anide(III) cations with 3D supramolecular framework structures, [La(DMSO)(8)][PW12O40] (1) and [La(DMSO)(8)][PMo12O40] (2) (DMSO = dimethyl sulfoxide), have been synthesized in aqueous solution under moderate conditions and further characterized by elemental analysis, inductively coupled plasma (ICP) analyses, IR spectroscopy, electronic spectra, thermogravimetric analysis, and single-crystal X-ray diffraction analyses. The title complexes exhibit similar 3D supramolecular frameworks directed by the different hydrogen bonding interactions. The TG curve exhibit the weight loss of complex 1, which can be divided into five stages, suggesting that the intensity of coordination bonds are different between La(III) and DMSO molecules.