Employing hybrid HF/DFT functional in conjunction with the relativistic effective core potential for Pu atoms and all-electron basis set 6-311g（d） for O atoms, the equilibrium geometrical structures of PuO, PuO2 and Pu2O3 molecules are obtained in the geometry optimization. The infrared and Raman spectra are also calculated. The bond lengths and harmonic vibration frequencies of ground states of PuO and PuO2 molecules are all in agreement with available experimental data. In geometry optimization of Pu2O3 molecule, we have tested more than twenty initial structures with different spin multiplicities （1, 3, 5, 7, 9, 11 and 13）. A C2v geometry corresponding to electronic state of 11B2 is considered as the ground state of Pu2O3 molecule. The harmonic frequency, IR intensity, Raman scatting activity and depolarization ratio of Pu2O3 molecule are obtained for the first time in theory. The vibrational modes corresponding to the maximum peaks are assigned for PuO2 and Pu2O3 molecules. In all studied molecules, the charge transfers from Pu to O atoms are found from natural bonding orbital analysis （NBO）. Relative to PuO and PuO2 molecules corresponding to Pu-O single- bond, the interactions between Pu and O in Pu2O3 are much weaker. The spin magnetic moments of studied molecules stem mainly from the 5f atomic orbitals of Pu atoms, but for O atoms the antiparallel spins from 2p atomic orbital are exhibited.