  The thermal entanglement in a two-qubit Heisenberg \emph{XXZ} spin chain is
investigated under an inhomogeneous magnetic field \emph{b}. We show that the
ground-state entanglement is independent of the interaction of
\emph{z}-component $J_{z}$. The thermal entanglement at the fixed temperature
can be enhanced when $J_{z}$ increases. We strictly show that for any
temperature \emph{T} and $J_{z}$ the entanglement is symmetric with respect to
zero inhomogeneous magnetic field, and the critical inhomogeneous magnetic
field $b_{c}$ is independent of $J_{z}$. The critical magnetic field $B_{c}$
increases with the increasing $|b|$ but the maximum entanglement value that the
system can arrive becomes smaller.
