The natural refrigerant $CO_2$has attracted as an alternative refrigerant currently used in air conditioning system, which has high global warming potential. In this study, the tribological characteristics of the sliding surfaces between a fixed scroll and an orbiting scroll of the scroll compressor were investigated in $CO_2$/ POE mixed environment. The pin-on-disk type sliding tests were carried out under the various sliding speeds, normal loads. surface roughness, and pressures. During the test, friction forces, wear amount and surface temperature were monitored.