  We propose to realize Weyl semimetals in a cubic optical lattice. We find
that there exist three distinct Weyl semimetal phases in the cubic optical
lattice for different parameter ranges. One of them has two pairs of Weyl
points and the other two have one pair of Weyl points in the Brillouin zone.
For a slab geometry with (010) surfaces, the Fermi arcs connecting the
projections of Weyl points with opposite topological charges on the surface
Brillouin zone is presented. By adjusting the parameters, the Weyl points can
move in the Brillouin zone. Interestingly, for two pairs of Weyl points, as one
pair of them meet and annihilate, the originial two Fermi arcs coneect into
one. As the remaining Weyl points annihilate further, the Fermi arc vanishes
and a gap is opened. Furthermore, we find that there always exists a hidden
symmetry at Weyl points, regardless of anywhere they located in the Brillouin
zone. The hidden symmetry has an antiunitary operator with its square being
$-1$.
