Compressors can be divided into volumetric compressors and velocity compressors according to their principles. Volumetric compressors are divided into reciprocating compressors and rotary compressors; Speed compressors are divided into axial compressors, centrifugal compressors, and mixed flow compressors.

　　Nowadays, compressors for household refrigerators and air conditioners are of the positive displacement type, which can be further divided into reciprocating and rotary types. Reciprocating compressors use piston, crank, connecting rod mechanisms or piston, crank, sliding tube mechanisms, while rotary compressors mostly use rolling rotor compressors. In commercial air conditioning, there are mostly centrifugal, vortex, and screw types.

　　According to the application scope, it can be divided into low back pressure type, medium back pressure type, and high back pressure type. Low back pressure (evaporation temperature -35~-15 ℃), generally used for household refrigerators, food freezers, etc. Medium back pressure type (evaporation temperature -20~0 ℃), generally used for cold drink cabinets, milk refrigerators, etc. High back pressure type (evaporation temperature -5~15 ℃), generally used for room air conditioners, dehumidifiers, heat pumps, etc.