Two-stage centrifugal compressor

The utility model provides a two-stage centrifugal compressor which comprises a first centrifugal compressing device, a second centrifugal compressing device and a connecting shaft. The second centrifugal compressing device is arranged on the lower portion of the first centrifugal compressing device and is communicated with the first centrifugal compressing device; the first centrifugal compressing device and the second centrifugal compressing device are respectively and fixedly arranged on the connecting shaft. According to the two-stage centrifugal compressor, the connecting shaft provides driving force for the first centrifugal compressing device and the second centrifugal compressing device, air is output from the first centrifugal compressing device into the second centrifugal compressing device and further pressurized, so that the pressure ratio of the centrifugal compressor is improved, and therefore the requirement of an engine is satisfied. The two-stage centrifugal compressor is simple in structure, small in number of parts, low in manufacturing cost and high in reliability and maintainability.