In order to analyze the influence of different loading rates on the mechanical properties of socket-type flexible interface under monotonous loading mode, the monotonous loading test of socket-type flexible interface of ductile iron pipelines under DN150 mm bending action is carried out, and based on the bending moment and rotation angle, rotation angle and pull-out displacement data, the general law of the bending moment-rotation angle-axial displacement relationship of the flexible interface is established, and a concise mathematical expression is given. The test results show that: (1) When the angular displacement of the interface does not reach the contact angular displacement, the loading rate has little influence on the bending moment value of the interface; After the interface angular displacement follows the contact angular displacement, the bending moment value of the interface is significantly affected by the loading rate. 2) When the contact angular displacement is less than 2°, it is mainly extrusion deformation; 2° ~ 4.7° (contact angular displacement) is mainly frictional resistance and partial extrusion deformation; The contact angular displacement is greater than 4.7° to the loading stop, which is mainly the frictional resistance. The results can provide some references for the seismic design and construction of flexible interface pipelines.