  Using the quasi-normal modes frequency of near extremal Schwarzschild-de
Sitter black holes, we obtain area and entropy spectrum for black hole horizon.
By using Boher-Sommerfeld quantization for an adiabatic invariant $I=\int
{dE\over \omega(E)}$, which $E$ is the energy of system and $\omega(E)$ is
vibrational frequency, we leads to an equally spaced mass spectrum. In the
other term we extend directly the Kunstatter's approach [7] to determine mass
and entropy spectrum of near extremal Schwarzschild-de Sitter black holes which
is asymptotically de Sitter rather than asymptotically flat.
