Since the electroluminescence in polymer comes from the transportation and combination of carriers in the electric field,it is essential to study the polarization property of the excitation in polymer.First we obtain the analytic solutions of exciton and biexciton,then their polarizabilities are calculated using the Green function method.An important result is that we analytically proved that the polarizability of the exciton is positive and that of the biexciton is negative.It follows that the polarization will be reversed when the exciton becomes biexciton.