  Topological semimetals recently stimulate intense research activities.
Combining first-principles calculations and effective model analysis, we
predict that CaTe is topological node-line semimetal when spin-orbit coupling
(SOC) is ignored. We also obtain the nearly flat surface state which has the
drumhead characteristic. When SOC is included, three node lines evolve into a
pair of Dirac points along the $M-R$ line. These Dirac points are robust and
protected by $C_{4}$ rotation symmetry. Once this crystal symmetry is broken,
the Dirac points will be eliminated, and the system becomes a strong
topological insulator.
