  We construct a three family flipped SU(5) model from the heterotic string
theory compactified on the $\Z_{12-I}$ orbifold with one Wilson line. The gauge
group is $\rm SU(5)\times U(1)_X\times U(1)^2\times[SU(2)\times SO(10)\times
U(1)^2]^\prime$. This model does not derive any nonabelian group except SU(5)
from $E_8$, which is possible only for two cases in case of one shift $V$, one
in ${\bf Z}_{12-I}$ and the other in ${\bf Z}_{12-II}$. We present all possible
Yukawa couplings. We place the third quark family in the twisted sectors and
two light quark families in the untwisted sector. From the Yukawa couplings,
the model provides the R-parity, the doublet-triplet splitting, and one pair of
Higgs doublets. It is also shown that quark and lepton mixings are possible. So
far we have not encountered a serious phenomenological problem. There exist
vectorlike flavor SU(5) exotics (including \Qem=$\pm\frac16$ color exotics and
\Qem=$\pm\frac12$ electromagnetic exotics) and SU(5) vectorlike singlet exotics
with \Qem=$\pm\frac12$ which can be removed near the GUT scale. In this model,
${\rm sin}^2\theta_W^0={3/8}$ at the full unification scale.

High Energy Physics - Theory;High Energy Physics - Phenomenology