  It is commonly believed that a careful investigation of the subleading terms
is crucial for a better understanding of the $QCD$ factorization in charmless B
decays. In this work the penguin-dominated $B\to K\pi$ decays are discussed
systematically, including the subleading corrections in $1/m_b$ due to soft and
hard gluons, besides the annihilation contributions. Soft-gluon effects for all
the relevant 4-quark effective operators are calculated within the framework of
the light-cone QCD sum rules (LCSR). Our observation is that such soft and hard
corrections are less important than the annihilation effects, enhancing only
the branching ratios by a few percent; the resultant increase in the branching
ratios due to the overall ${\cal O}(1/m_b)$ effects is between about $(22-27)%$
of the QCD factorization results with the ${\cal O}(\alpha_s)$ corrections, as
the weak phase $\gamma (=\textmd{Im}V_{ub}^*)$ ranges from $40^0$ to $80^0$.
Impacts of the involved uncertainties are discussed in some details.
