A reducing support ring for a bridge plug and a bridge plug for sealing or packing boreholes or wells. The reducing support ring for the bridge plug includes a ring-shaped body with a setting surface provided on a circumferential outer wall or end face of the ring-shaped body. Deformation of the ring-shaped body under an axial compression force allows the setting surface of the ring-shaped body to be abutted against and positioned on an inner wall of a sleeve where a bridge plug is located and to form a surface contact-type sealed connection with the inner wall of the sleeve. The bridge plug includes the reducing support ring. The reducing support ring and the bridge plug improve the plugging effect and anchoring performance of the bridge plug and the convenience of construction.