  In this article, we study the contribution from the final-state interactions
to the strong coupling constant $g_{D^* D \pi}$. We take an assumption that the
momentum transfers in the strong decay $D^{*+} \to D^0 \pi^+$ be large to
validate the operator product expansion in the light-cone QCD sum rules. At
large momentum transfers, the final-state interactions play an important role,
and we should take them into account.
