  We calculate the contributions to the rare decays $B \to X_{s,d} \nu \bar
\nu$ and $B_{s,d} \to l^+l^-$ from one-loop $Z^0$-penguin diagrams in the
framework of Topcolor-assisted Technicolor Model. Within the parameter space,
we find that: (a) the new contribution from technipions is less than 2% of the
standard model prediction; (b) the top-pions can provide a factor of 10 to 30
enhancement to the ratios in question; (c) the topcolor-assisted technicolor
model is consistent with the current experimental data.
