A theoretical method to calculate multidimensional Fmnck-Condon factors including Duschinsky effects is described and used to simulate the photoelectron spectroscopy of the anion O₃^-. Geometry optimization and harmonic vibrational frequency calculations have been performed on the X ¹A₁ state of O₃^- and X ²B₁ state of O₃^-. Franck-Condon analyses and spectral simulation were carried out on the first photoelectron band of O₃^-. The theoretical spectrum obtained by employing CCSD(T)/6-311+G(2d,p) values are in excellent agreement with the observed one. In addition, the equilibrium geometry parameters, rε(OO)=0.1355+0.0005 nm and θε(O-O-O)=114.5+0.5^{°, of the X2B1 state of O₃-, are derived by employing an iterative Franck-Condon analysis procedure in the spectral simulation.}