  Three dimensional (3D) Dirac semimetal is a novel state of quantum matter,
characterized by the gapless bulk four-fold degeneracy near Fermi energy. Soon
after its discovery, the classification of stable 3D Dirac semimetals with
inversion and rotational symmetry have been studied. However, only ten out of
thirty-two point groups have both inversion and rotational symmetry, and we
need a more complete classification of stable 3D Dirac semimetals. Here we
classify stable 3D Dirac semimetals with reflection symmetry and rotational
symmetry in the presence of time reversal symmetry, which belong to seventeen
different point groups. These systems include the systems preserving inversion
symmetry except $\mathrm{C_{3i}}$. They have two classes of reflection
symmetry, with the mirror plane parallel to rotation axis and the mirror plane
perpendicular to rotation axis. In both cases two types of Dirac semimetals are
determined by four different reflection symmetries. The first type of Dirac
semimetals will appear through accidental band crossing (ABC). The second type
of Dirac semimetals have a Dirac point at a time reversal invariant momentum
(TBC). We show that in both mirror parallel and perpendicular cases, $C_{2,3}$
symmetry can only protect stable Dirac points via TBC, while $C_{4,6}$ symmetry
can have stable Dirac points as ABC or TBC. We further discuss that Weyl line
nodes and Dirac semimetal can exist in Brillouin zone at the same time using
$\mathrm{C_{4v}}$ symmetry as an example. Finally we classify Dirac line nodes
and Weyl line nodes to show in which types of mirror plane they can exist.
