  In this paper, by investigating the factor of the $x^n+1$, we deduce that the
structure of the reversible negacyclic code over the finite field
$\mathbb{F}_{q}$, where $q$ is an odd prime power. Though studying
$q-$cyclotomic cosets modulo $2n$, we obtain the parameters of negacyclic BCH
code of length $n=\frac{q^\ell+1}{2}$ , $n=\frac{q^m-1}{2(q-1)}$ and
$n=\frac{q^{t\cdot2^\tau}-1}{2(q^t+1)}$. Some optimal linear codes from
negacyclic codes are given. Finally, we discuss a class of MDS LCD negacyclic
codes.
