  The QCD corrections to the top-quark pair production via both polarized and
unpolarized gluon fusion in $pp$ collisions are calculated in the Minimal
Supersymmetric Model(MSSM). We find the MSSM QCD corrections can reach 4% and
may be observable in future precise experiments. Furthermore, we studied the CP
violation in the MSSM, our results show that the CP violating parameter is
sensitive to the masses of SUSY particles (It becomes zero, when the c.m.
energy is less than twice the masses of both gluino and stop quarks.) and may
reach $10^{-3}$.
