A diffuser and volute are formed between the volute cover plate and the volute base plate, and the diffuser is connected to the volute. The impeller is rotatably discharged gas through the diffuser and the gas is discharged from the diffuser to the volute and then discharged from the centrifugal compressor. The diffuser adjustment assembly includes a driving ring, a driving rod, a pin and a diffuser ring. The radial assembly is disposed in an inner circumference surface of the driving ring. The axial assembly is disposed between an outer circumference surface, a top surface and a bottom surface of the driving ring. The drive assembly is used to rotatably drive the driving ring to rotate. When the driving ring is rotated, the driving rod is moved by the pin moving to the pin track of the driving ring to drive the diffuser ring to adjust a flow path width of the diffuser.