The invention discloses a wedge-shaped hole packer for liquid carbon dioxide phase change rock breaking. An inner cylinder (2) is a cylinder with the gradually increased thickness, and at least two inner cylinder vertical seams (21) are symmetrically formed in the upper portion of the inner cylinder (2); an outer cylinder (3) is a cylinder with the gradually decreased thickness, and at least two outer cylinder vertical seams (31) are symmetrically formed in the lower portion of the outer cylinder (3); the inner cylinder (2) is higher than the outer cylinder (3) and is sleeved with the outer cylinder (3), the two ends of the inner cylinder (2) and the two ends of the outer cylinder (3) are each provided with a small section of stretching part, the stretching parts do not make contact with one another, and two rope tying holes (6) are symmetrically formed in the stretching part arranged on the top of the inner cylinder (2). After the inner cylinder and the outer cylinder are combined together, the two ends of the inner cylinder and the two ends of the outer cylinder are each provided with a small section of stretching part, and the stretching parts do not make contact with one another; the inner cylinder stretches out for a small section, so that the rope tying holes are exposed to tension a wedge-shaped cylinder, and the outer cylinder stretches out for a small section, so that gas is gathered to push the inner cylinder to move upwards relative to the outer cylinder. According to the wedge-shaped hole packer, the structure is simple, operation is easy and convenient, and walls of a fracturing pipe and a fracturing hole are locked according to a wedge shape geometry principle, so that the fracturing hole achieves leakproofness and airtightness; accordingly, the rock breaking effect is enhanced, and pipe flashing is prevented.