<p>In an era of the early Universe at a time estimated to be a millionth<br>of a second after the Big Bang, the Universe was filled with quark-gluon plasma. In<br>this plasma and due to the high temperature the strong coupling constant, that characterizes<br>the magnitude of the strong force acting on quarks and gluons, becomes so<br>small. As a consequence quarks and gluons inside this plasma can be considered as<br>an ideal gas of gluons and massless quarks that weakly interact with each others.<br>Thus, for this plasma, one can describe its characteristics by the equations of states<br>that relate both energy density and pressure to its temperature. This has been done<br>in several models in the literature with the recent information about the properties<br>of the quark-gluon plasma provided by relativistic heavy-ion collision experiments<br>and some astrophysical measurement. In this article we review three of these models<br>namely the MIT bag model, Model 1 and Model 2. Moreover, we solve Einstein’s<br>field equations of the general relativity,that describe our universe, to show the time<br>evolution of energy density, pressure and temperature in the early universe in these<br>three models. This kind of a study is important as our present universe evolved from<br>a universe filled with quark-gluon plasma<br></p>