With energy consistent method for ion XY⁺(ECMI),three-order analytical potential energy function ECMI(3)for diatomic molecular ion XY⁺ is expanded to five-order ECMI(5)potential.ECMI(5)potential is used to study potential energy curves (PEC)of diatomic molecular ion XY⁺:B²Σ⁺ state of CO⁺ and b⁴Σ^- state of SO⁺.It overcomes shortcoming of Morse potential or Huxley-Murrell-Sorbie(HMS)potential.1.hey are neutral diatomic molecular potential energy functions and can not be always correct for potential energy functions of diatomic molecular ion XY⁺.ECMI(5)potential shows excellently agreement with Rydberg-Klein-Bees(BKB)data.Higher-order ECMI potential generates reliable potential energy data in total area,including important asymptotic and dissociation regions where relative experimental data may be absence or quantum theoretical results may not be reliable.