Abstract: Strong acceleration effect has an obvious influence on the convective heat transfer to supercritical carbon dioxide flowing in a heated tube. Acceleration parameter (A) is an important dimensionless number to represent the level of acceleration effect quantitatively. In the process of developing acceleration parameter, carbon dioxide state equation is needed. The difference was analyzed, caused by choosing of different state equations, the ideal state equation or van der Waals equation. The evaluation, with the help of experimental data, shows that A_van-der (based on van der Waals equation) is able to predict the local deteriorated heat transfer as a result of strong flow acceleration better than A_ideal (based on ideal state equation). Analysis showed that the volumetric expansion factor and the volumetric compression factor, with which the acceleration factor should be developed, indicate the essence of acceleration effect.