The Coulomb bound potential effects on the parabolic linear bound potential quantum dot qubit were studied under the condition of electron-LO-phonon strong coupling using the variational method of Pekar type. The numerical results lead us to formulate the derivative relationship of the probability density of electron in superposition state of the ground state and first-excited state with the Coulomb binding parameter, confinement length and electron-LO-phonon coupling strength, respectively.