  In this paper, we study the degeneracies among several cosmological
parameters in detail and discuss their impacts on the determinations of these
parameters from the current and future observations. By combining the latest
data sets, including type-Ia supernovae "Union2.1" compilation, WMAP seven-year
data and the baryon acoustic oscillations from the SDSS Data Release Seven, we
perform a global analysis to determine the cosmological parameters, such as the
equation of state of dark energy w, the curvature of the universe \Omega_k, the
total neutrino mass \sum{m_\nu}, and the parameters associated with the power
spectrum of primordial fluctuations (n_s, \alpha_s and r). We pay particular
attention on the degeneracies among these parameters and the influences on
their constraints, by with or without including these degeneracies,
respectively. We find that $w$ and \Omega_k or \sum{m_\nu} are strongly
correlated. Including the degeneracies will significantly weaken the
constraints. Furthermore, we study the capabilities of future observations and
find these degeneracies can be broken very well. Consequently, the constraints
of cosmological parameters can be improved dramatically.
