  On the basis of the first law of black hole thermodynamics, we propose the
concept of effective temperature of de Sitter (dS) black holes and conjecture
that the effective temperature should be the temperature of the dS black holes
when the Hawking radiation temperatures of the black hole horizon and the
cosmological horizon are equal. Choosing different independent variables, we
can find a differential equation satisfied by the entropy of the dS black hole.
It is shown that the differential equation of entropy is independent of the
choice of independent variables. From the differential equation, we get the
entropy of dS black hole and other effective thermodynamic quantities. We also
discuss the influence of several parameters on the effective thermodynamic
quantities.
