A centrifugal compressor includes a volute base block, a volute cover plate, an impeller, a diffuser-adjusting assembly, a radial constraint assembly, an axial constraint assembly and a driving assembly. A diffuser and a connected volute are formed between the cover plate and the base block. The impeller discharges gas to the centrifugal compressor through the diffuser and the volute. The diffuser adjustment assembly includes a driving ring, a driving rod, a pin and a diffuser ring. The radial constraint assembly is disposed on an inner circumference surface of the driving ring. The axial constraint assembly on an outer circumference surface of the driving ring is located between the top and bottom portions. The drive assembly is to rotate the driving ring. When the driving ring rotates, the pin slides along the pin track, and the driving rod displaces the diffuser ring to adjust a flow-path width of the diffuser.