A centrifugal compressor, comprising: a shell, which has a fluid inlet and a fluid outlet, the fluid inlet being located at a top of the shell; a motor assembly, which is arranged in the shell and comprises a stator and a rotor, the rotor comprising a vertically arranged rotor shaft, and the rotor shaft comprising a lower end and an upper end; a centrifugal compression mechanism, an impeller (41, 44) of which is connected with the rotor shaft so as to be driven by the motor assembly, wherein the centrifugal compression mechanism is arranged downstream of the fluid inlet to receive a fluid, compress and pressurize the fluid, and output the pressurized fluid in a direction away from the motor assembly; and a guide member, which receives the pressurized fluid from the centrifugal compression mechanism, and which defines a flow passage alone or together with a part of the shell, wherein the flow passage is configured such that all of the pressurized fluid from the centrifugal compression mechanism passes through and cools the motor assembly and is discharged from the fluid outlet; wherein the guide member is a pipe and wherein the guide member has a first end connected to an output port of the centrifugal compression mechanism, a second end connected to a side wall of the shell, such as a lower part of the side wall of the shell, and a pipe body connected between the first end and the second end and comprising a curved part (531, 532); characterised in that: the second end extends into the shell and is aligned with an opening at a bottom of a motor housing of the motor assembly such that a gap is defined between the second end and the opening; a first portion of the pressurized fluid passes from the second end into the opening and through a first pathway within the motor housing; and a second portion of the pressurized fluid passes from the second end through the gap and through a second pathway between the motor housing and the shell. a shell, which has a fluid inlet and a fluid outlet, the fluid inlet being located at a top of the shell; a motor assembly, which is arranged in the shell and comprises a stator and a rotor, the rotor comprising a vertically arranged rotor shaft, and the rotor shaft comprising a lower end and an upper end; a centrifugal compression mechanism, an impeller (41, 44) of which is connected with the rotor shaft so as to be driven by the motor assembly, wherein the centrifugal compression mechanism is arranged downstream of the fluid inlet to receive a fluid, compress and pressurize the fluid, and output the pressurized fluid in a direction away from the motor assembly; and a guide member, which receives the pressurized fluid from the centrifugal compression mechanism, and which defines a flow passage alone or together with a part of the shell, wherein the flow passage is configured such that all of the pressurized fluid from the centrifugal compression mechanism passes through and cools the motor assembly and is discharged from the fluid outlet; wherein the guide member is a pipe and wherein the guide member has a first end connected to an output port of the centrifugal compression mechanism, a second end connected to a side wall of the shell, such as a lower part of the side wall of the shell, and a pipe body connected between the first end and the second end and comprising a curved part (531, 532); characterised in that: the second end extends into the shell and is aligned with an opening at a bottom of a motor housing of the motor assembly such that a gap is defined between the second end and the opening; a first portion of the pressurized fluid passes from the second end into the opening and through a first pathway within the motor housing; and a second portion of the pressurized fluid passes from the second end through the gap and through a second pathway between the motor housing and the shell. the second end extends into the shell and is aligned with an opening at a bottom of a motor housing of the motor assembly such that a gap is defined between the second end and the opening; a first portion of the pressurized fluid passes from the second end into the opening and through a first pathway within the motor housing; and a second portion of the pressurized fluid passes from the second end through the gap and through a second pathway between the motor housing and the shell.