The invention discloses a composite material of a common outer medical air-conditioning machine shell and a preparation method of the composite material. The composite material consists of the following components in parts by weight: 50-100 parts of polypropylene, 20-40 parts of polyphenylene sulfide, 5-20 parts of a light reflector, 5-10 parts of carbon nanotubes, 5-10 parts of a coupling agent, 0.1-1 part of an antioxidant, 1-2 parts of a lubricant and 0.2-0.6 part of a flame retardant. As polypropylene and polyphenylene sulfide are commixed, the thermoplasticity and the mechanical strength are improved, in addition, good heat conductivity, oxidation resistance and light reflection are achieved, sunshine can be prevented from radiating into a machine shell, and the temperature inside the machine shell is effectively reduced in summer.