An axial flow compressor, in its simplest form, consists of a number of rotating blade rows fixed to a rotating drum. The drum rotates inside and air tight casing to which are fixed stator blade rows. The blades are made of aerofoil section to reduce the loss caused by turbulence and boundary separation. As the drum rotates, the air flows through the alternately arranged stator and rotor. The flow of air is parallel to the axis of compressor.

In an axial flow compressor, the ratio of pressure in the rotor blades to the pressure rise in the compressor in one stage is known as degree of reaction. The type of rotary compressor used in gas turbines, is of axial flow type.

The compressor capacity is defined as the volume of air delivered by the compressor, and is expressed in m³/min or m³/s.