  One of the great triumphs of the inflationary model is the prediction of the
flat power spectrum of the CMB fluctuation. The prediction is based on the
assumption of the de-Sitter vacuum in the past infinity. However, the true past
infinity of the inflation is expected to be dominated by radiation and
curvature of the space. We consider pre-inflation era as dominated by radiation
and curvatures as well as inflation potential. We derive the exact solutions
for the scalar fields in this era and find a exact power spectra caused by the
inflaton vacuum fluctuation. We show that the power spectrum is almost flat for
sub-horizon scale and deviates from flat for very high super-horizon
fluctuation, which is quite sensitive to the radiation and the curvature in the
pre-inflation era.
