  In the minimal supersymmetric standard model, we have studied the evolution
of the neutrino flavor mixing by using the renormalization group equation(RGE)
with the Georgi-Jarlskog texture for the Yukawa coupling matrices.For the large
Yukawa coupling of the charged lepton, i.e.,$\tan\b \gg 1$, the neutrino flavor
mixing increases significantly with running down to the electroweak scale by
the RGE. If one wishes to get the large neutrino flavor mixing $\sin \th_{23}$
at the electroweak scale, which is suggested by the muon neutrino deficit in
the atomospheric neutrino flux, the initial condition $\sin \th_{23}\geq 0.27$
is required at the GUT scale. Combined with the see-saw enhancement of the
neutrino flavor mixing, the large mixing is naturally reproduced by setting the
reasonable initial condition.
