Reflecting the economical potential and research value of LNG pipeline transportation, through the comparison of the cost of LNG tank and pipeline. By analyzing the calculation accuracy and scope of application of LNG and Hydrocarbon mixtures of AGA8-DC92, Traditional cubic equation of state and GERG_2008, to highlight the behavior of high precision and wide-range. With the study of leaking process and diffusion model, to show two commonly method: DEGADIS and Heavy gas cloud box model. Enumerate hydrocarbon fluid throttling process usual P-R method, and summed thermodynamic analysis system of LNG and LNG-like mixtures, based on GERG_2008.