Abstract: The paper introduces several domestic and international common desiccating techniques on long distance gas pipelines. They are the desiccant method, the flowing gas vaporizing method and the vacuum desiccating method. It compares these methods' merits and shortcomings, and briefly introduces their application at home. Besides, it makes a main introduction to the common using dry air desiccating method, including its basic principles, typical craft processes and how to produce the dry air. This paper analyzes all kinds of factors that may affect this method and briefly explains the dry air's standard and something needed to be focused on.