  Using the next-to-leading order low energy effective Hamiltonian for $|\Delta
B|=1$, $\Delta C=\Delta U=0$ transitions, the contributions of electroweak
penguin operators in $ B^-(\overline {B_d^0})\rightarrow PP$ and $PV$ decays
are estimated in the standard model. We find that, for some channels, the
electroweak penguin effects can enhance or reduce the QCD penguin and/or tree
level contributions by at least $30\%$, and can even play dominant role.
