With the construction and production of Shaanxi-Beijing gas pipeline II and Ⅲ, China-Asian gas pipeline, West-East gas pipeline , the second Shaanxi-Beijing and the third West-East gas pipeline ,there is large differential pressure between high pressure trunk line and urban distribution pipeline. It is an economic and sufficient way to utilize differential pressure to liquefy natural gas by expansion refrigeration. In this paper, domestic existing pipe natural gas liquefaction plant was analyzed,it’s found that there were some defects in the liquefaction plant ,then the liquefaction plant was improved. The improved process can adapt to all kinds of differential pressure(>3.0~3.5 MPa), especially when the differential pressure is beyond the critical pressure. At the same time, the improved pipe natural gas process was analyzed. The influence of some essential parameters (such as split ratio, cryogenic gas temperature and pressure) on liquefying rate was investigated. Finally, the improved process was optimized, and the liquefying rate reached 19.86%. The results show that the improved pipeline liquefied natural gas process can make full use of differential pressure, and has a high liquefying rate and strong adaptability to pressure.% 陕京二、三线、西一线、中亚管道、西二线相继投产以及西三线全面开工，国内输气管道操作压力等级越来越高。沿线高压管道与城市配气管网之间存在很大压差，在调峰型 LNG 站中利用压差膨胀制冷液化天然气是一种经济利用压力能方案。对国内现存的一种管道天然气液化装置分析，发现存在不合理性并对其改进，改进后流程能够适应各种压差（>3.0~3.5 MPa）特别是克服了当压力大于临界压力时不能正常有效工作的缺陷。同时对改进的管道天然气液化装置进行研究分析，得出该装置的关键参数（如：分流器分流比、膨胀机膨胀压力、低温天然气温度等）对整个液化率的影响。最后对改进的管道天然气液化装置优化分析得出各物流参数并且液化率达到19.86%。由此可见改进的管道液化天然气装置具有充分利用压能、液化率高和适应范围广等优点。
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