Abstract: In the first replacement and commissioning process of Hengqin-Macau Gas Pipeline, the method in foam pig's pigging, 48-hour purging with air compressor and nitrogen replacement was adopted, but failed to meet the drying requirements. Based on the analysis and comparison of flowing gas evaporation method, vacuum drying method, and desiccant drying method, the advantages of the desiccant drying method, especially desiccant retained within the pipe can inhibit hydrate for long time, TEG+liquid nitrogen purge drying scheme was recommended to used in the subsequent drying. According to the specific drying requirements and the actual situation of the pipeline, this paper calculates the dewatering and drying water volume, TEG consumption volume and drying time, provides the drying operation steps and acceptation flow of sealing stability and analyzes the cause for common failures and puts forward treatment measures.