  Loop quantum cosmology (LQC) is very powerful to deal with the behavior of
early universe. And the effective loop quantum cosmology gives a successful
description of the universe in the semiclassical region. We consider the
apparent horizon of the Friedmann-Robertson-Walker universe as a
thermodynamical system and investigate the thermodynamics of LQC in the
semiclassical region. The effective density and effective pressure in the
modified Friedmann equation from LQC not only determine the evolution of the
universe in LQC scenario but are actually also found to be the thermodynamic
quantities. This result comes from the energy definition in cosmology (the
Misner-Sharp gravitational energy) and is consistent with thermodynamic laws.
We prove that within the framework of loop quantum cosmology, the elementary
equation of equilibrium thermodynamics is still valid.
