  Assuming the lightest neutralino forms dark matter, we study its residual
annihilation after freeze-out at the early universe. If taking place after the
big bang nucleosynthesis (BBN) the annihilation products, especially at the
hadronic modes, may cause nonthermal nuclear reaction and change the prediction
of the primordial abundance of light elements in the standard BBN scenario. We
therefore put constraints on the neutralino annihilation cross section. These
constraints are free of the uncertainties of the dark matter profile today
suffered by direct or indirect detection of dark matter. We find the
constraints by BBN is important, especially when taking large $\tan\beta$. If
the light element abundances can be determined with higher precision in the
future the constraint will become very strong, so that a majority of the
parameter space allowed by the relic density requirement may be excluded.
