Abstract: Accurate calculation of natural gas compressibility(Z) is of great significancc. Here dealt with in the article are guite a few metbods to calculate the compressibi- lity that bave been raised over since 1940s, and the comments on them respectively.For the natural gas containing a little non-hydrocarbon, the absolute mean deviation made by S-K graphic solution is 3%, lower in accuracy than those made in some other ways. With the wide application of electronic computing techinique, the me- thods for calculation of (Z) with state equations are quickly developing, of which R-K. equation is more frequently used, which is of high accuracy in the Case of the natural gas containing little non-bydrocarbon or heavy hydrocarbon. In the case of the natural gas with more CO2 and H2S, such methodg as mentioned above may be satisfactory.if proved via critical temperature.