The conventional calculation models of electron displacement polarizability are summarized and their limitations are revealed.Following the analysis

a new calculation model is developed

which takes the effect of the induced dipole moment of one atom on the polarizability into consideration

and the mathematical expressions are deduced in the cases of macro electric field parallel and perpendicular to the molecular axis

and at a random angle with the axis. The electron displacement polarizabilities in the hexagonal boron nitride(h-BN)crystal are evaluated by the new model.The results are compared with those from the classical models to point out the applied scope of the new model.