  Neutrino oscillation is phenomenon of random transition from a flavor state
of neutrino to another, and should obey quantum statistics theory, and
constitutes Markoffian process. The process is depicted by method of CTRW
(continuous time random walk), and the time-evolution formula of flavor
distribution of neutrino beam has been established. The simulation with
Markoffian model for solar and cosmic ray neutrino indicates neutrino
oscillation will arrive at equilibrium flavor distribution of three-fold
maximum if propagation time is long enough, which is consistent to the data of
SK and SNO experiments.
