Abstract: This paper reports the SCC investigation on 3 gas transmission pipelines (1 pipeline over 30 years old and 2 newly-installed pipelines) in western and middle China. For the old pipeline, the author reviews the failure cases and corrosion investigation collected in past years and excavated dozens of sites aiming at detecting soil environment, anti-corrosion coating, cathodic protection and corrosion of pipe surface, analyzes the reasons why SCC does not occur in oil pipeline yet. For 3 pipelines, the author evaluates the SCC sensitivity of line pipe steels in typical soil environment by using slow strain rate tests and other experiments. For the pipelines in western China, the author also analyzes the soil environment and operation pressure fluctuation. This paper summaries some conditions that are prone to SCC and present measures of SCC prevention based on the analytical results.