  Vacuum structure and related phenomenological features are investigated in
$\mu$-problem solvable supersymmetric extra U(1) models. We present a framework
for the analysis of their vacuum structure taking account of an abelian gauge
kinetic term mixing, which can potentially modify a scalar potential and $Z^0$
gauge interactions. Applying this to data of the precise measurements at LEP,
we constrain an allowed region in a space of Higgs vacuum expectation values
based on consistency with potential minimum conditions. We find that such a
region is confined into rather restricted one. Bounds on masses of an extra
U(1) gauge boson and the lightest neutral Higgs boson are predicted.
Renormalization group equations for gauge coupling constants and gaugino soft
masses in an abelian gauge sector are also discussed in relation to the gauge
kinetic term mixing in some detail.
