Two compounds of organic molybdate-alkali salt: [H(4,4'-bipy)]2[K2Mo8O26](I) and H3 [Na Mo8 O26] (4,4'-bipy)5 (H2O)4 (II), with beta-[Mo8O26]4- anion, were synthesized. The relationship between their properties and structures was studied by using FTIR, Raman, NIR-Vis and fluorescence etc. They possess isolating beta-[Mo8O26]4- anion, whose terminal O atoms combine with alkali. The FTIR and Raman spectra showed that the vibrational frequencies of the group are related to the structure of the materials. In UV-Vis spectra of compound (I) and (II), there is a characteristic wide peak at 280-300 nm. The fluorescence spectra of compound (I) and (II) were studied, which showed that the wide emission peak is from 450 to 650 nm and excited by 350 nm for compound (I), and the emission peak is from 400 to 550 nm and excited by 325 nm for compound (II). For compound (I), the intensity of emission becomes stronger with decreasing of temperature, and so does the fluorescence lifetime.