The problems of an electron bound in a hydrogenic impurity and interacting with the longitudinal optical phonon field of an ionic crystal or a polar semiconductor have been of considerable interest. Since To-kuda investigated the problem of bound polaron by using variational scheme of the Lee-Low-Pines theory

many investigators studied the properties of the bound polaron by means of various theoretical methods and experimental methods. Lepine et al. studied the properities of bound polaron in a narrow-band polar crystal within the scheme of effective-mass approximation. Chen et al. studied properties of bound polaron in parabolic quantum wire by using the Feynmann-Haken path-integral approach.Liang et al. investigated binding energy of bound polaron in ternarg mixed crystals

taking into account the interaction of an electron with two branch longitudinal optical phonon.Es-sbai studied LO phonons effect on the binding energy of impurity bound polaron in 3D GaAs quantum dot by using variational method. Molnikov discussed the effect of the electron-phonon interaction on an electron bound to an impurity in a spherical quantum dot by using adiabatic variational method. Devreese studied properities of bound polaron in oxide compounds by using quantum-chemical method.The properties of a strong or a weak coupling bound magnetopolaron was discussed by using a linear combination operator and a unitary transformation methods by the present authors. In the past

most work was devoted at zero temperature.In fact

the case of a finite temperature is more significant.However

the temperature dependence of the properties of bound polaron has not been studied so far.In this paper

the temperature dependence of effective mass of bound optical polaron which is in a strong or a weak-coupling with optical phonon was calculated by using improved linear combination operator and unitary transformation method. Numerical calculations

for the RbCl crystal

as an example

are pertormed and the results illustrate that the vibrational frequency and the effective mass of the strong-coupling bound polaron increase with increasing the temperature and the Coulomb potential.