The invention provides a plasma cleaning method, a packaging method, a power module and an air conditioner. The plasma cleaning method includes carrying out plasma cleaning on a substrate and/or the power module by the aid of mixed gas with oxygen and argon. The flow range of the oxygen is 0-500 sccm, the flow range of the argon is 0-200 sccm, the radiofrequency power range is 0-1000 W in plasma cleaning procedures, and the substrate and/or a power device are close to an excitation end or a ground end in a plasma cleaning cavity. According to the technical scheme, the plasma cleaning method, the packaging method, the power module and the air conditioner have the advantages that dust and organic matters such as soldering flux and viscose on the substrate can be effectively removed, binding force between the substrate and packaging materials can be increased, surface stress on contact surfaces of the substrate and a packaging shell can be reduced, accordingly, the power module is stable in structure, and the heat dissipation performance, the humidity-resistant and heat-resistant performance and the reliability of the power module further can be improved.