We study the effects of the fourth quark generation model in Bs→π^-K^＋ decay. Combining with the up-to-date experimental measurement for B（Bs→π^-K^＋） dir - and Acp ^dir（Bs→π^-K^＋） by the CDF Collaboration, we derive the new bound of weak phase Фbd, which are 0° 〈 Фbd 〈 44°,321° 〈 Фbd 〈 360° and 0° 〈 Фbd 〈 26°, 342° 〈Фbd 〈 360° for mr, ： 400 and 600 GeV respectively. In these regions, B（Bs→π^-K^＋） and Acp^dir （Bs→π^-K^＋） consist with the current experimental data within errors.
