  Recently, the vacuum energy of the QCD ghost in a time-dependent background
is proposed as a kind of dark energy candidate to explain the acceleration of
the universe. In this model, the energy density of the dark energy is
proportional to the Hubble parameter $H$, which is the Hawking temperature on
the Hubble horizon of the Friedmann-Robertson-Walker (FRW) universe. In this
paper, we perform a constraint on the ghost dark energy model with and without
bulk viscosity, by using the Markov Chain Monte Carlo (MCMC) method and the
combined latest observational data from the type Ia supernova compilations
including Union2.1(580) and Union2(557), cosmic microwave background, baryon
acoustic oscillation, and the observational Hubble parameter data.
