  With plasma shielding effects of the Debye-H\"uckel model, we investigate the
relativistic photoionization processes of H, Nb$^{40+}$ and Pb$^{81+}$ plasmas
in the H-isoelectronic series. The shielded nuclear potential of Yukawa-type
experienced by the electron is parameterized by Debye-length $D$. To account
for relativistic effects non- perturbatively, we solve the Dirac equation for
the bound as well as continuum wavefunctions. Contributions from multipole
fields are calculated for high incident photon energies, while the angular
distribution and spin polarization parameters of photoelectrons are provided in
the electric-dipole approximation. Our results of photoionization cross
sections for the H plasma agree with other available theoretical calculations.
The interplay between the relativistic and plasma shielding effects on the
photoionization parameters is also studied. \keywords{Photoionization,
Multipole effect, Debye plasma, Hydrogen atom, Hydrogen-like ions
