Molybdenum is one of elements concentrated in power reactor high-level waste liquid. The dissolution of MoO3 in iron phosphate glass and the influence of MoO3 content on glass structure are the focus of researches on the iron phosphate glass formulation for immobilizing power reactor high-level waste liquid. To investigate the dissolution of MoO3 in iron phosphate glass and the effect of MoO3 content on the glass structure, a series of 60% P2O5-19%Fe2O3-8%Al2O3-13%Na2O(in mole fraction, the same below) samples doped with MoO3 at different ratios (i.e., 1%-8%) were prepared by a melting-quenching method. The phase and microscopic morphology were analyzed by X-ray diffraction (XRD) and electron probe microanalysis (EPMA). The structure of the samples was characterized by Raman spectroscopy, X-ray photoelectron spectroscopy (XPS) and Mssbauer spectroscopy. Molybdenum can be completely dissolved into the glass structure without forming the crystallite and phase separation when the actual content of MoO3 is less than 6.38%. Molybdenum exists mainly in the form of ［MoM6］ octahedral in the glass, and Mo-O-P bonds are observed with the MoO3 content of more than 4%. The Q1 and Q2 units are the main structures in the glass phase, and the relative content of the Q1 unit increases with MoO3 doping content. The content of Fe3+ decreases slightly, while the valence state of Mo ions remains unchanged with the increase of MoO3 doping content.