  The possibility of CP violation is studied in the Higgs sector of a
supersymmetric standard model with multiple Higgs singlets. The tree-level
Lagrangian in this model is assumed to conserve the CP symmetry. We find that
CP violation is viable in this model at the one-loop level, in an explicit way,
if the radiative corrections from the third generation of quarks and squarks
are taken into account. In the presence of explicit CP violation, at the
one-loop level, the upper bound on the mass of the lightest neutral Higgs boson
and the productions of the neutral Higgs bosons via the Higgsstrahlung process
in high-energy $e^+e^-$ collisions are calculated. We find that the upper bound
on the mass of the lightest neutral Higgs boson increases as the number of
Higgs singlets increases in a regulated manner. The production cross sections
of the neutral Higgs bosons also show a reasonable increasing behavior with
respect to the number of Higgs singlets.
