  The charmless bottom meson decays are systematically investigated based on an
approximate six quark operator effective Hamiltonian from perturbative QCD. It
is shown that within this framework the naive QCD factorization method provides
a simple way to evaluate the hadronic matrix elements of two body mesonic
decays. The singularities caused by on mass-shell quark propagator and gluon
exchanging interaction are appropriately treated. Such a simple framework
allows us to make theoretical predictions for the decay amplitudes with
reasonable input parameters. The resulting theoretical predictions for all the
branching ratios and CP asymmetries in the charmless $B^0, B^+, B_s\to \pi\pi,
\pi K, KK$ decays are found to be consistent with the current experimental data
except for a few decay modes. The observed large branching ratio in $B\to
\pi^0\pi^0$ decay remains a puzzle though the predicted branching ratio may be
significantly improved by considering the large vertex corrections in the
effective Wilson coefficients. More precise measurements of charmless bottom
meson decays, especially on CP-violations in $B\to K K$ and $B_s\to \pi\pi, \pi
K, KK$ decay modes, will provide a useful test and guide us to a better
understanding on perturbative and nonperturbative QCD.
