The invention discloses a multiple-cylinder rotating compressor and a compressing mechanism thereof. The compressing mechanism comprises at least two air cylinders, pistons, sliding blades, center spacers and an extension spring piece, wherein the pistons can circularly roll in compressing cavities of the air cylinders, the sliding blades can slidably move back and forth in sliding grooves of theair cylinders, and the center spacers are arranged between the two adjacent air cylinders. The extension spring piece comprises one or two semicircular main body segments, and the main body segments are located between the two adjacent air cylinders and circle the center spacers half cycle, fixing parts and executing parts are correspondingly arranged at the two ends, corresponding to each other in the radial direction, of the length of the main body segments. The fixing parts are located on the air cylinders or the center spacers, and the executing parts drive the sliding blades to connect with the pistons in an abutting mode frequently. The compressing mechanism can not only improve the rigidity of the air cylinders, but also can improve the leak problem of a refrigerant.