The invention discloses a cylinder body structure of a heat engine, and particularly relates to an efficient cooling engine cylinder. The efficient cooling engine cylinder comprises a cylinder body with high-pressure working medium gas expansion inside, an inner cavity of the cylinder body is provided with a jacket embedded on the inner wall of the cylinder body, the jacket is provided with a fluid inner cavity, and a cooling flow way is formed in the fluid inner cavity and is connected with a high-pressure oil cooler and a pressurizing device. By the adoption of the structure, the jacket with a circular cooling channel is arranged in the inner cavity of the cylinder body, the circular cooling channel is sequentially in series connection with a high-pressure oil cooler and the pressurizing device or directly connected with the high-pressure oil cooler and the pressurizing device, and accordingly through introducing of high-pressure cooling oil into the circular cooling flow way, the oil pressure and the pressure of high-pressure working media in the inner cavity of the cylinder body are equivalent; thus, the thickness of the inner cylinder wall can be smaller, the temperature brought by wear between a piston ring and the inner cylinder wall can be absorbed, and according to the efficient cooling cylinder body of the heat engine, no matter how much the thickness of the cylinder body is increased, the cooling effect is not affected.