  We investigate the effect of chiral phase transition on the pentaquark
$\Theta^+$ mass and width at one-loop level of $N\Theta^+K$ coupling at finite
temperature and density. The behavior of the mass, especially the width in
hadronic medium is dominated by the characteristics of chiral symmetry
restoration at high temperature and high density. The mass and width shifts of
positive-parity $\Theta^+$ are much larger than that of negative-parity one,
which may be helpful to determine the parity of $\Theta^+$ in high energy
nuclear collisions.
