  We show that the desirable weak mixing angle sin^2 theta_W = 0.2312 at m_Z
scale can be generated naturally in the SU(3)_C times SU(3) model on M^4 times
S^1 / (Z_2 times Z_2') where the gauge symmetry SU(3) is broken down to SU(2)_L
times U(1)_Y by orbifold projection. For a supersymmetric model with a TeV
scale extra dimension, the SU(3) unification scale is about hundreds of TeVs at
which the gauge couplings for SU(3)_C and SU(3) can also be equal in the mean
time. For the non-supersymmetric model, SU(2)_L times U(1)_Y are unified at
order of 10 TeV. These models may serve as good candidates for physics beyond
the SM or MSSM.
