Abstract: As the physical parameters of liquid ammonia are greatly influenced by its volume expansibility and temperature sensitivity, the gas blocking phenomenon easily occurs in liquid ammonia pipelines due to the gasification of liquid ammonia. In order to explore the hydraulic and thermal characteristics of liquid ammonia pipelines, the simulation model of long-distance liquid ammonia pipelines was established with the correction of physical parameters of ammonia based on the actual design and operation parameters of existing liquid ammonia pipeline in China. The influences of pipe diameter, ambient temperature, outlet pressure, inlet temperature, flow rate and soil medium on the hydraulic and thermal characteristics of liquid ammonia pipelines were simulated and analyzed. The results show that, with the increase of pipe diameter, the downward trend of pressure in the whole pipeline gradually becomes flat. When the ambient temperature is lower than the inlet temperature of the pipeline, the phase change of liquid ammonia can be effectively avoided by the appropriate increase of pipe diameter. On the basis of comprehensive consideration of pipeline pressure and liquid ammonia expansibility, appropriately increasing pipeline pressure can effectively reduce the risk of liquid ammonia gasification. At low flow rate, the increase of flow rate has little influence on the pressure drop and great influence on the temperature drop in liquid ammonia pipelines, while the conclusion is opposite at high flow rate. The research results are expected to provid a reference for the design and safe operation of ammonia pipeline.