O-shaped ring assembling device

The invention relates to the technical field of O-shaped ring assembling, in particular to an O-shaped ring assembling device which comprises a sleeve, a mandrel and an elastic part. The sleeve is provided with a through hole penetrating in the axial direction, a sliding groove penetrating through the hole wall of the through hole in the radial direction and an annular groove formed in the peripheral face of the sleeve in the circumferential direction and used for containing an O-shaped ring. The through hole comprises a large-diameter hole with a large diameter and a small-diameter hole witha small diameter, a step surface is formed between the large-diameter hole and the small-diameter hole, the sliding groove and the annular groove are formed in the end, away from the large-diameter hole, of the small-diameter hole, and the end, away from the large-diameter hole, of the sliding groove penetrates through the annular groove in the axial direction; the mandrel is movably arranged in the through hole in the ax