The utility model discloses a composite casing rubber stopper for well cementation. The composite casing rubber stopper for well cementation comprises a core bar, multiple rubber discs and guide heads. The core bar is sleeved with the rubber discs and the guide heads. A positioning mechanism fixing every two adjacent rubber discs to the core bar is arranged between every two adjacent rubber discs. Each positioning mechanism comprises a pair of rubber disc fixing bases, a C-shaped elastic retainer ring and a rectangular clamping groove formed in the outer wall of the core bar. Each rubber disc fixing base is in a cylinder shape, the core bar is right sleeved with the inner diameter of each rubber disc fixing base, a first expanded diameter is formed at one top end of each cylindrical inner cavity, the outer wall of each rubber disc is right sleeved with the diameter of the corresponding first expanded diameter, a second expanded diameter is formed at the other top end of each cylindrical inner cavity, each pair of rubber disc fixing bases are symmetrically utilized so that the two corresponding second expanded diameters can form an annular groove with a rectangular section, a through groove with a rectangular section is formed by each annular groove and the corresponding clamping groove formed in the outer wall of the core bar, and each C-shaped elastic retainer ring is inserted into the corresponding through groove so that the two corresponding adjacent rubber discs can be fixed to the core bar. All rubber disc systems are independent of each other, so the situation that the whole rubber stopper falls into pieces due to the fact that one rubber disc is damaged cannot occur. The composite casing rubber stopper for well cementation has the advantages of being high in strength and stability and the like.