It is necessary to calculate natural gas thermophysical property parameters in the water power and thermodynamic calculation of pipelines. The method of solving each physical property parameter of natural gas and solving process were introduced in detail. The compression factor of nitrogen gas was obtained by using Van der Waals equation, RKS equation, P-R equation and BWRS equation respectively. It is concluded from the comparison of the experiment data that as a two-parameter cubic equation, the P-R has more accuracy than that of the Van der Waals and the RKS equation, but slightly lower accuracy than that of BWRS equation. But P-R equation has less number of parameters and is easier to compute and determine parameters. Therefore, the P-R equation gets an extensive application in the area of thermophysical property calculation.