  Negacyclic BCH codes are an important subclass of negacyclic codes and are
the best linear codes in most cases, but their parameters are hard to
determine. In this paper, we mainly study two types of negacyclic BCH codes of
length $n=\frac{q^{m}-1}{4},\frac{q^{m}+1}{4}$, and give their dimensions and
the lower bound on their minimum distance. Furthermore, we provide the weight
distribution of narrow-sense neagcyclic BCH codes of length $n=\frac{q^m-1}{4}$
for some special designed distances.
