Abstract: During commissioning process of Phase Ⅰ Project of Sichuan-East Gas Transmission Pipeline, for the purpose of ensuring normal production of Xinqingxi No. 1 Well, emergency commissioning was carried out for Chuanwei Subline. In nitrogen sealed isolation sections, Yanziwo-Tiansheng Section and Tiansheng-Jinshan Section, it adopted "gas-togas" replacement process to carry out synchronous replacement for the process pipelines in compressor stations and longdistance pipeline. Regulating valves in the valve chamber were used to regulate the flow, control the replacement speed and relieve the casing pressure in oil reservoir of the gas well. It adopted interconnecting back transmission process flow for trunkline and sub-line and utilized the gas remaining in the pipeline to ensure the smooth commissioning of Puguang Purification Plant with. This paper describes the key control points and technical measures in the pipeline commissioning and replacement process in detail through specific analysis of operation parameters, such as nitrogen injection, displacement, boost, flow control, etc.