Due to its single function and low flexibility, the existing emergency rescue equipment is difficult to meet the requirements of complex emergency operations under geological disasters such as earthquake. To solve this problem, an electromechanical hydraulic quick coupling device, which can realize fast change of attachments and free adjustment of posture, is designed. The device can be quickly integrated into emergency rescue equipment to complete high-mobility and multi-function rescue tasks. In the investigation, first, the extreme load characteristics, as well as the stress and strain situations during the operation of the device are simulated and analyzed, through which the weak part and load spectrum are determined. Then, the reliability theoretical models considering cyclic damage strength degradation under deterministic and random periodic stress are deduced and established, and the mapping relationship between the reliability and the failure rate of the rotating mechanism is determined. Furthermore, based on linear elastic fracture mechanics, the crack propagation of the weak part of inclined oil cylinder's piston rod is analyzed, and the fatigue life of the device is determined via the local stress strain method to ensure that the device can meet the application requirements. Finally, the developed device is integrated into the walking rescue robot. Test results show that the proposed quick coupling device can realize the rapid switching of various attachments such as bucket and gripper, with a switching time of less than 15 s, as well as the increases by ±40° yaw and ±360° rotation degrees of freedom, thus meeting the requirements of flexible operation. This research provides theoretical reference for the design of similar devices.