The invention belongs to the technical field of engines, particularly relates to the technical field of engine manufacturing and discloses a rotor and round air cylinder engine. According to the rotor and round air cylinder engine, a rotor is adopted to rotate in a round air cylinder, and the working cycle of air suction, compression, burst and exhaust is finished by means of stretching and retracting of sliding sheets. The rotor and round air cylinder engine is characterized in that four rectangular notches are uniformly and axially formed in the cylindrical rotor, a lubricating oil hole is drilled in the bottom end of each notch, and the sliding sheets are placed in the notches and stretch and retract outwards under the action of vertical expansion pieces and centrifugal force; a lubricating oil hole is drilled in the axis of the rotor cylinder, eight accelerator grooves are formed in the outer side of the rotor cylinder, and a supporting base is arranged on a circulation support of the engine; an upper mold penetrating rod and a lower mold penetrating rod are arranged on each engine station on the supporting base in the diagonal direction and are perpendicular to the supporting base, wherein the lower end of the upper mold penetrating rod and the lower end of the lower mold penetrating rod are hinged through a connecting rod; the lower mold penetrating rods are connected through transmission connecting rods, and one lower mold penetrating rod is provided with a handle.