  The gauge kinetic mixing in general is allowed in models with multiple
Abelian gauge groups. In this paper, we investigate the gauge kinetic mixing in
the framework of $U(1)$ extensions of the MSSM. It enlarges the viable
parameter space, and has an important effect on the particle mass spectrum as
well as the $Z_2$ coupling with matters. The SM-like Higgs boson mass can be
enhanced with a nonzero kinetic mixing parameter and the muon $g-2$ tension is
slightly less severe than in the case of no mixing. We present the results from
both benchmark analysis and global parameter scan. Various theoretical and
phenomenological constraints have been considered. The recent LHC searches for
the $Z_2$ boson are important for the case of large positive kinetic mixing
where the $Z_2$ coupling is enhanced, and severely constrain scenarios with
$M_{Z_2} < 2.8$ TeV. The viable dark matter candidate predicted by the model is
either the neutralino or the right-handed sneutrino. Cosmological constraints
from dark matter searches play a significant role in excluding the parameter
space. Portions of the parameter space with relatively low sparticle mass
spectrum can be successfully explored in the LHC run-2 as well as future linear
colliders and dark matter searches.
