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We calculate the decay constants of Ds and D ∗ s with B̄ 0 → D+l−ν and B̄0 → D+D s decays. In our analysis we take the factorization method with considering non-factorizable term contributions and used two different form factor behaviours (constant and monopoletype) for F0(q 2). We also consider the QCD-penguin and Electroweak-penguin contributions in hadronic decays within the NDR renormalization scheme at NLO calculation. We estimate the decay constant of the Ds meson to be 233 ± 49 MeV for (pole/pole)-type form factor and 255±54 MeV for (pole/constant)-type form factor. For D s meson, we get fD∗ s = 346± 82 MeV, and fD∗ s/fDs = 1.43 ± 0.45 for (pole/constant)-type form factor. PACS index : 12.15.-y, 13.20.-v, 13.25.Hw, 14.40.Nd Keywards : Factorization, Non-leptonic Decays, Decay Constant, Penguin Effects Email: [email protected] † Email: ccthmail.kek.jp; Monbusho Fellow in Japan