  In this paper, we calculate the branching ratios for B^0\to D_s^+\pi^-,
B^+\to D_s^+\pi^0, B^0\to D_s^{*+}\pi^- and B^+\to D_s^{*+}\pi^0 decays in the
perturbative QCD factorization approach. We find that the calculated branching
ratios of these four decay channels agree well with the measured values and
current experimental upper limit. In the numerical calculation, we take the
decay constant and the shape parameter of the vector meson D^{*}_s as
f_{D^{*}_s}=312 MeV and a_{D^{*}_s}=0.78 respectively, which are larger than
those in the previous calculations.
