  We re-express the Kerr metric in standard Bondi-Saches' coordinate near null
infinity ${\cal I}^+$. Using the uniqueness result of characteristic initial
value problem, we prove the Kerr metric is the only asymptotic flat,
stationary, axial symmetric, Type-D solution of vacuum Einstein equation. The
Taylor series of Kerr space-time is expressed in terms of B-S coordinates and
the N-P constants have been calculated.
