In order to analyze the influence of loading rate on the functional performance of the socket flexible pipeline interface, this article conducted monotonic loading tests on three loading rates of ductile iron pipeline socket flexible interface under bending action with a diameter of DN300 mm. Before the interface angular displacement reached the ultimate angular displacement, the influence of loading rate was relatively small. However, after the ultimate angular displacement, the magnitude of the interface bending moment value was significantly affected by the loading rate, and there was no water leakage phenomenon when the loading was stopped. Based on experimental data, MATLAB analysis software was used to analyze the data of water pressure, angle, angle, and pull-out displacement inside the pipe. A three-dimensional model was established, in which the relationship between water pressure inside the pipe, interface angle, and interface axial displacement follows a general law. The following conclusion can be drawn: 1) The article defines the ultimate turning angle of DN300 mm pipe diameter as 5.8° ; 2) A concise mathematical expression was given for the relationship between water pressure inside the pipe, interface angle, and interface axial displacement. The fitting curve of water pressure inside the pipe and interface angle was compared, and the fitting results were basically consistent with the experimental results; 3) It has been proven that the flexible pipeline interface has good water supply performance during the loading process.