  We study the thermodynamic properties of Schwarzschild-de Sitter (SdS) black
hole and Reissner-Nordstr\"{o}m-de Sitter (RNdS) black hole in the view of
global and effective thermodynamic quantities. Making use of the effective
first law of thermodynamics, we can derive the effective thermodynamic
quantities of de Sitter black holes. It is found that these effective
thermodynamic quantities also satisfy Smarr-like formula. Especially, the
effective temperatures are nonzero in the Nariai limit, which is consistent
with the idea of Bousso and Hawking. By calculating heat capacity and Gibbs
free energy, we find SdS black hole is always thermodynamically stable and RNdS
black hole may undergoes phase transition at some points.
