Abstract: External-corrosion prevention design is significant during the gas long distance pipeline design, and it also has a direct relation to the service life of pipelines. This article introduces present situation on the external-corrosion prevention design for long distance pipelines at home and abroad. It also analyzes the characteristics of anti-corrosion materials commonly used. Aimed at the external-corrosion prevention design in complex terrain, the authors bring forward the design points, that is, environment and construction condition, proper coating materials on the basis of techno-economic analysis.