Abstract: Pressure lead-in pipe used in compressor stations and valve chambers of West-to-East Gas Transmission Pipeline is characterized by small diameter with thin pipe wall and easy to leak when pressure is increased.In allusion to this problem, technical improvement to the pressure lead-in pipes of the whole pipeline with on-line stoppling technology is made.Scenarios in on-line stoppling technology for small— diameter pressure lead-in pipe and improvement steps are introduced, and risk factors possibly existed during the improvement are considered and suitable scope for on-line stoppling technology is provided.The wal! thickness for improved pressure lead-in pipe is increased to 5 mm, which effectively ensure the safety in pipeline operation.