A cold ring-rolling machine for small and medium sized ring spares is characterized in that the cold ring-rolling machine is provided with a stander structure (26) that can prevent the stander from becoming deformed and improve the structure and layout of a rib plate. A rounded roll milling wheel structure, an over-locating small slide rod structure, a workpiece supporting wheel structure, a following circularity roller adjusting structure for workpiece circularity, a principal slide rod structure and a feeding drive mechanism are arranged on the stander. The roll-milling wheel (25) of the rounded roll milling wheel structure is arranged on a principal axis (24) and the principal axis (24) is connected with a principal axis seat (28) through four sets of cylindrical-roller bearings. The small slide rod (8) of the over-locating small slide rod structure is arranged on the open mouth fork. The support (12) of the workpiece supporting wheel structure is linked with the principal slide rod (21) of the feeding drive mechanism. The gyration center of the following circularity roller adjusting structure for workpiece circularity and the principal axis (24) are concentric.