  Considering the octet baryons in relativistic mean field theory and selecting
entropy per baryon S=1, we calculate and discuss the influence of U boson on
the equation of state, mass-radius, moment of inertia and gravitational
redshift of massive protoneutron star (PNS). The effective coupling constant
$g_{U}$ of U bosons and nucleons is selected from 0GeV$^{-2}$ to 70GeV$^{-2}$.
The results point that U bosons will stiffen the equation of state (EOS). The
influence of U bosons on the pressure is more obvious at low density than high
density, while, the influence of U bosons on the energy density is more obvious
at high density than low density. The U bosons play a significant role in
increasing the maximum mass and radius of PNS. When the value of $g_{U}$
changes from 0GeV$^{-2}$ to 70GeV$^{-2}$, the maximum mass of massive PNS
increases from 2.11 $M_{\odot}$ to 2.58 $M_{\odot}$, and the radius of PNS
corresponding PSR J0348+0432 increases from 13.71 km to 24.35 km. The U bosons
will increase the moment of inertia and decrease the gravitational redshift of
PNS. For PNS of the massive PSR J0348+0432, the radius and moment of inertia
vary directly with $g_{U}$, the gravitational redshift vary inversely with
$g_{U}$ approximately.
