Abstract: R290, as an effective and environmentally friendly refrigerant, has great potentials in the application of air-conditioning. In this paper, the performance of inverter air conditioner (AC) using R290 was compared theoretically with that of other refrigerants. Moreover, the performance of a split AC was experimentally studied in both summer and winter conditions with different ambient temperatures. Results show that the performance of R290 AC system is theoretically higher than that of R410A and R32, which is comparable to R134a. In winter condition, the system energy efficiency ratio (EER) varies from 3.78 to 2.79 as the ambient temperature changes from 12 ℃ to -12 ℃; in summer condition, the system EER decreases from 2.26 to 1.91 as the indoor temperature increases from 29 ℃ to 43 ℃, with a relatively constant cooling power at about 1.5 kW. The discharge temperature of inverter AC using R290 is far lower than that of R32. However, there is still great potential for improvement of supply air temperature control. This study provides reference for optimization of inverter AC using R290.