The invention discloses a three-dimensional (3D) mechanical probe, which comprises a sound window, a base, a restraining body and an elastic sealing ring, wherein the sound window and the base are fixedly connected and form a sealed space, the sound window is provided with a first matching wall, the base is provided with a second matching wall, the first matching wall is sheathed with the second matching wall, the sealing ring is arranged between the first matching wall and the second matching wall and is tightly pressed to deform, and the restraining body limits the deformation of the sound window. Through the sealing ring with the compression deformation quantity between the first matching wall and the second matching wall, the sealing between the sound window and the base can be effectively ensued, the coupling liquid seepage is prevented, through the arrangement of the restraining body, the sound window is prevented from deforming through being expanded by the sealing ring, the sufficient deformation quality of the sealing ring is ensued, and the sealing performance between the base and the sound window is further ensured.