The invention mainly relates to a compression energy obtaining method and unique design of cylinders. Through a multi-cylinder rotary structure designing method, work doing advantages are integrated, the energy source and compression energy conservation serves as a center, and the purpose of low-rotation-speed and high-power output power is achieved. Low-boiling point liquid mainly serves as media, and compression energy is obtained in a heating mode by the utilization of physical properties of vaporization and liquefaction of the low-boiling point liquid for outwards doing work. In the method, a multi-cylinder rotary steam-driven engine with multiple cylinders for doing work is included, internal energy of the compression energy can be fully and completely released, and the multi-cylinder rotary steam-driven engine is a steam-driven engine with the center of saving energy sources and the purpose of low-rotation-speed and high-power output. As the principle of the steam-driven engine is the same as the principle of an internal combustion engine, through the advantages, the method can also be applied to the multi-cylinder rotary internal combustion engine with the multi-cylinder rotary steam-driven engine as the principle, the multi-cylinder rotary steam-driven engine and the multi-cylinder rotary internal combustion engine are in the multi-cylinder doing-work mode, the purposes of saving the compression energy and energy sources is achieved through low-rotation-speed and high-power output and displacement reduction, and the multi-cylinder rotary steam-driven engine and the multi-cylinder rotary internal combustion engine are far superior to current traditional internal combustion engines and steam-driven engines in working principle. By application of the working principle, a hydraulic oil cylinder can be used as a component for doing work, and the output power of the compression energy is greatly increased.