  In the framework of the topcolor-assisted technicolor ($TC2$) model and the
littlest Higgs model with $T$-parity ($LHT$ model), we consider the rare B
decays $B\to M\nu\bar{\nu}$ with $M=\pi,K,\rho,$ or $K^{\ast}$. We find that
the contributions of the $TC2$ model to the branching ratios of these decay
processes are larger than those for the $LHT$ model. The experimental upper
limits for some branching ratios can give severe constraints on the free
parameters of the $TC2$ model.
