Characteristics　of　NVH　(Noise,　vibration　and　harshness)　in　twin　screw　refrigeration　compressors,　mainly　caused　by　mechanical　vibration　and　turbulent　gas　flow,　are　discussed　in　detail.　According　to　the　different　generation　mechanism,　suppression　methods　of　mechanical　NVH　and　hydrodynamic　NVH　are　proposed,　respectively.　Mechanical　NVH　is　related　to　rotor　profile,　bearings,　lubricating　conditions　and　maching　precision,　while　hydrodynamic　NVH　is　inevitable　and　severe　for　all　positive　displacement　compressors　due　to　gas　compression　and　turbulent　flow.　Concluded　from　three　cases　of　NVH　suppression　for　semi-hermetic　twin　screw　refrigeration　compressors,　half-wave　method　based　on　acoustic　interference　theory,　pulsation　damper　evolving　from　Helmholtz　resonator　and　broadband　perforated　tube　silencer　are　effective　paths　to　alleviate　hydrodynamic　NVH　in　twin　screw　refrigeration　compressors　without　bringing　in　extra　energy　losses.　©　Published　under　licence　by　IOP　Publishing　Ltd.