A centrifugal compressor, comprising multiple stages of compression units which are communicated in sequence, each stage of compression unit comprising: a diffusion cavity; and a diffusion cavity adjustment device, the diffusion cavity adjustment device comprising a movable member configured to change a flow area of the diffusion cavity provided in correspondence thereto, and the movable member being movably provided in an axial direction of the centrifugal compressor; wherein each stage of diffusion cavity adjustment device further comprises: a transmission rod, the transmission rod being in drive connection with the corresponding movable member; and a guide structure, fixedly connected with a cavity wall of the corresponding diffusion cavity, the transmission rod being movably provided in the axial direction of the centrifugal compressor with respect to the guide structure; the centrifugal compressor further comprises: an air inlet; being characterised in that the centrifugal compressor further comprises a plurality of inlet guide blades, provided at the air inlet; a drive device, the drive device being in drive connection with the inlet guide blades; and a plurality of transmission shafts, each of the transmission shafts being in drive connection with the drive device respectively, the transmission shafts being in drive connection with the inlet guide blades in a one-to-one correspondence manner, the transmission rod of the compression unit closest to the air inlet being in transmission connection with one of the corresponding transmission shafts, and the transmission rod of each of the remaining stages of compression units being in transmission connection with the movable member of the previous stage of compression unit. a diffusion cavity; and a diffusion cavity adjustment device, the diffusion cavity adjustment device comprising a movable member configured to change a flow area of the diffusion cavity provided in correspondence thereto, and the movable member being movably provided in an axial direction of the centrifugal compressor; wherein each stage of diffusion cavity adjustment device further comprises: a transmission rod, the transmission rod being in drive connection with the corresponding movable member; and a guide structure, fixedly connected with a cavity wall of the corresponding diffusion cavity, the transmission rod being movably provided in the axial direction of the centrifugal compressor with respect to the guide structure; the centrifugal compressor further comprises: an air inlet; being characterised in that the centrifugal compressor further comprises a plurality of inlet guide blades, provided at the air inlet; a drive device, the drive device being in drive connection with the inlet guide blades; and a plurality of transmission shafts, each of the transmission shafts being in drive connection with the drive device respectively, the transmission shafts being in drive connection with the inlet guide blades in a one-to-one correspondence manner, the transmission rod of the compression unit closest to the air inlet being in transmission connection with one of the corresponding transmission shafts, and the transmission rod of each of the remaining stages of compression units being in transmission connection with the movable member of the previous stage of compression unit. a transmission rod, the transmission rod being in drive connection with the corresponding movable member; and a guide structure, fixedly connected with a cavity wall of the corresponding diffusion cavity, the transmission rod being movably provided in the axial direction of the centrifugal compressor with respect to the guide structure; the centrifugal compressor further comprises: an air inlet; being characterised in that the centrifugal compressor further comprises a plurality of inlet guide blades, provided at the air inlet; a drive device, the drive device being in drive connection with the inlet guide blades; and a plurality of transmission shafts, each of the transmission shafts being in drive connection with the drive device respectively, the transmission shafts being in drive connection with the inlet guide blades in a one-to-one correspondence manner, the transmission rod of the compression unit closest to the air inlet being in transmission connection with one of the corresponding transmission shafts, and the transmission rod of each of the remaining stages of compression units being in transmission connection with the movable member of the previous stage of compression unit. an air inlet; being characterised in that the centrifugal compressor further comprises a plurality of inlet guide blades, provided at the air inlet; a drive device, the drive device being in drive connection with the inlet guide blades; and a plurality of transmission shafts, each of the transmission shafts being in drive connection with the drive device respectively, the transmission shafts being in drive connection with the inlet guide blades in a one-to-one correspondence manner, the transmission rod of the compression unit closest to the air inlet being in transmission connection with one of the corresponding transmission shafts, and the transmission rod of each of the remaining stages of compression units being in transmission connection with the movable member of the previous stage of compression unit.