The invention discloses an air conditioning system, a compressor and an enthalpy increase assembly thereof. The enthalpy increase assembly comprises a part (91) with an enthalpy increase opening (912), and further comprises an enthalpy-increase check valve assembly (902), of which one end is connected to the main body (911) of the part (91), and the other end can cover the enthalpy increase opening (912) in an opened and closed manner. According to the enthalpy increase assembly provided by the invention, by arranging the enthalpy-increase check valve assembly at the enthalpy increase opening, enthalpy increase gas supplemented by a gas supplementation branch flows into the compressor from the enthalpy increase opening only, so that the problem of backflow of supplemented gas for enthalpy increase in the compressor is avoided, the flow resistance loss is reduced, the volume efficiency of the compressor is effectively improved, the performance of the compressor is improved, and the energy efficiency of an air conditioner is improved.