The potential energy function for ground state X5Σ- of the PuO molecule was worked out by the quadratic configuration interaction of single and double substitution method, based on the approximation of relativistic effective core potential for Pu atom and all-electron 6-311G* basis set for O atom. The calculated results for Re,De,Be,αe,ωe and ωeχe are 0.183nm,7.3909eV,0.3365,0.001642,781.15,and 2.77cm-1,respectively.In addition,the thermodynamic functions ΔH0,ΔS0，ΔG0 and Cp of the PuO(g) in standard state are also calculated,which are -118.88kJ/mol，96.16J/mol·K，-147.55kJ/mol,and 31.5656J/mol·K,respectively. All these results are in good agreement with the experimental data.