Aiming at the problem of large resistance loss along the pipeline when the ultra-long distance liquid supply system is used in the fully mechanized caving face, taking 122108 fully mechanized caving face of Wangzhuang Coal Mine as the research object, the relationship between the length, diameter and flow of the liquid supply pipeline and the pressure loss of the pipeline is simulated and analyzed by AMESim software. The results show that the longer the liquid supply distance, the greater the flow rate, the greater the pressure loss along the way ; the larger the diameter of the liquid supply pipeline, the smaller the pressure loss. At the same time, the field practice shows that when the liquid supply distance is 6 000 m, the main inlet and main return pipelines are respectively selected with the diameter of 133 mm and 159 mm lined with stainless steel alloy composite pipe for liquid supply, the pressure loss along the pipeline during the non-production period is about 1.5 MPa, and the pressure loss along the pipeline during the production period is about 2 ~ 3.5 MPa. The hydraulic support of the working face is in good condition, and there is no pipeline leakage and liquid channeling. The pressure of the whole hydraulic system can meet the actual production needs.