  We present a study of tau^- -> K^- pi^+ pi^- nu_tau decay using ~669 /fb
data, collected with the Belle detector at the KEKB asymmetric-energy e^+ e-
collider. The data is recorded at a center-of-mass energy 10.58 GeV. The result
for the branching ratio is : B = (3.25 +- 0.02(stat.) +0.16 -0.15(sys.))x10^-3
>. We also present results of the precise measurement of the branching ratio of
other 3-prong decay modes, tau^- -> pi^- pi^+ pi^- nu_tau, tau^- -> K^- K^+
pi^- nu_tau, and tau^- -> K^- K^+ K^- nu_tau .
