  We present a model of the lepton masses and flavor mixing based on the
discrete group $S_4 \times Z_2$. In this model, all the charged leptons and
neutrinos are assigned to the $3_\alpha$ representation of $S_4$ in the
Yamanouchi bases. The charged lepton and neutrino masses are mainly determined
by the vacuum expectation value structures of the Higgs fields. A nearly
tri-bimaximal lepton flavor mixing pattern, which is in agreement with the
current experimental results, can be accommodated in our model. The neutrino
mass spectrum takes the nearly degenerate pattern, and thus can be well tested
in the future precise experiments.
