  We show that the very light spin-1 gauge U-boson of the extra $U(1)'$ gauge
model in the framework of the supersymmetric standard model extension can be a
good candidate of the new light particle suggested by the HyperCP experiment.
We demonstrate that the flavor changing neutral currents (FCNCs) for the
HyperCP events in the decay of $\Sigma^{+}\to p \mu^{+} \mu^{-}$ can be
generated at both tree and loop levels. In particular, we find that the loop
induced $s\to d U$ transition due to the tensor-type interaction with the
dimension-5 electric dipole operator plays a very important role on the FCNCs.
Our explanation of the HyperCP data with the spin-1 U-boson is different from
that based on a light pseudoscalar Higgs boson or sgoldstino in the literature.
In particular, the U-boson involves a rich phenomenology in particle physics as
well as cosmology.
