A prosthetic mitral annuloplasty ring includes a wire, an adjustment member for changing a length of the wire and a jacketing annulus for adjusting a radial dimension of the mitral valve annuloplasty ring. The jacketing annulus is sleeved over the wire and forms, together with the adjustment member, a shape matching that of a native mitral valve annulus. After the prosthetic mitral annuloplasty ring is implanted by suturing in a conventional surgical procedure and the patient's heart starts to beat again, the adjustment member can be connected to the delivery device and the wire length therein can be adjusted by a rotating operation of the delivery device so that the mitral valve annuloplasty ring will be expanded or contracted until the prosthetic mitral annuloplasty ring perfectly fits the native mitral valve annulus in shape, effectively avoiding the problem of incomplete mitral leaflet coaptation.