  We predict branching ratios and CP asymmetries of the $B\to KK$ decays using
perturbative QCD factorization theorem, in which tree, penguin, and
annihilation contributions, including both factorizable and nonfactorizable
ones, are expressed as convolutions of hard six-quark amplitudes with universal
meson wave functions. The unitarity angle $\phi_3= 90^o$ and the $B$ and $K$
meson wave functions extracted from experimental data of the $B\to K\pi$ and
$\pi\pi$ decays are employed. Since the $B\to KK$ decays are sensitive to
final-state-interaction effects, the comparision of our predictions with future
data can test the neglect of these effects in the above formalism. The CP
asymmetry in the $B^\pm\to K^\pm K^0$ modes and the $B_d^0\to K^\pm K^\mp$
branching ratios depend on annihilation and nonfactorizable amplitudes. The
$B\to KK$ data can also verify the evaluation of these contributions.
