  We present a precise calculation of the lightest neutral Higgs boson
production associated with top quark pair at a linear collider. The full
one-loop electroweak ${\cal O}(\alpha_{ew})$ contributions to the process
$e^+e^- \to t\bar t h^0$ within the minimal supersymmetric standard model
(MSSM) are included. We analyze the dependence of the electroweak corrections
on the MSSM parameters such as $M_{A^0}$, $\tan\beta$, $M_2$, $A_{f}$,
$M_{SUSY}$ and $\mu$. The results show that the full one-loop electroweak
radiative corrections turn out to be about -20% quantitatively and thus are
important for future $e^+e^-$ linear colliders.
