The invention relates to an elastic coupling device of an ultrasonic testing probe. The elastic coupling device comprises a probe installation swing mechanism, the probe installation swing mechanism comprises a C-shaped arc frame and a bearing assembly, the C-shaped arc frame comprises two straight sections and an arc section for connecting the two straight sections, a probe is arranged between the two straight sections, the probe and the straight sections are in a rotation fit relationship, the arc section is inserted into the bearing assembly and rotates along an arc section extension direction, the outer side of each one of the straight sections of the C-shaped arc frame is connected to one end of an extension spring and the other end of the extension spring is connected to the outer side of the bearing assembly. The elastic coupling device can tightly contact with the surface to be detected so that the ultrasonic probe tightly clings to the detected surface filled with a coupling agent and the ultrasonic probe can self-adapt to curvature change of the detected surface and raised and pit parts of the surface in automatic scanning.