  We investigate the observational signatures of the holographic dark energy
model in this paper, including both the original model and a model with an
interaction term between the dark energy and dark matter. We first delineate
the dynamical behavior of such models, especially whether they would have a
"Big Rip" for different parameters, then we use several recent observational
data to give more reliable and tighter constraints on the models. The results
favor the equation of state of dark energy crossing -1, and the universe ends
in the "Big Rip" phase. By using the Bayesian evidence as a model selection
criterion to make the model comparison, we find that the holographic dark
energy models are mildly favored by the observations compared with the $%
\mathrm{\Lambda CDM}$ model.
