  Our aim is to investigate the thermodynamic properties of the universe
bounded by the cosmological event horizon and dominated by the tachyon fluid.
We give two different laws of evolution of our universe. Further, we show the
first law and the generalized second law of thermodynamics (GSLT) are both
satisfied in two cases, but their properties of the thermodynamic equilibrium
are totally different. Besides, under our solutions, we find the validity of
the laws of thermodynamics is irrelevant with the parameters of the tachyon
fluid. Finally, we conclude that the universe bounded by the cosmological event
horizon and dominated by the tachyon fluid has a good thermodynamic
description. In turn, the thermodynamic description can provide a good physical
interpretation for the dynamic evolution of our universe due to the equivalence
between the first law of thermodynamics and the Friedmann equation to some
extent.
