Refrigerant R134a (tetrafluoroethane) is widely used in automotive air conditioners and has a good performance. However, since refrigerant R134a still has a high global warming potential (GWP), this refrigerant must be replaced with environmentally friendly refrigerants such as R600a (isobutane), which is a natural fluid, no effect on the climate, inexpensive and readily available. In this study, thermodynamic analysis of a bus air conditioner working with refrigerant R600a was performed. Adana province of Turkey was chosen as the study region. Firstly, a bus used for inter-city passenger transportation with a passenger capacity of 56 persons was selected. Cooling Load Hourly Analysis Program (HAP) was used to determine the hourly cooling load capacity of the selected inter-city bus model. Useful and reversible works of compressor, coefficient of performance (COP), exergy efficiency and exergy destructions of the bus air conditioning system were obtained and evaluated in detail.