Abstract: Applicable equation of state to accurately calculate the nature of fluid and thermodynamic model is essentially needed. Expressions, solving process and steps and applicability of Soave-Redlich-Kwong (SRK), Peng-Robinson (PR) and Benedict-Webb-Rubin-Starling (BWRS) currently used in pipeline simulating are reviewed. It is considered that the 3 equations of state have sound applicability. Characteristics in SRK, PR and BWRS are analyzed and compared. Results display that BWRS is the most reasonable equation of state in simulating gas transmission pipelines.