Background: Exposure to air pollutants can cause many problems, including the health effects in humans and animals. The aim of this study was to assay the air quality in the Shiraz city during 2011-2013.

Methods: In this descriptive-analytical study, the air pollutant data during the study period were taken from Air Quality Co. for two main stations i.e. Darvazeh Kazeroun and Imam Hossein and then were analysed to determine air quality index.

Results: The maximum (0.018 ppm) and minimum (0.015 ppm) annual concentration of SO₂ were determined in 2011 and 2013, respectively. The maximum NO₂ concentration was measured in summer 2011 with a value of 0.025 ppm. Regarding ozone, the highest average concentration was measured in the summer season of 2013 with the concentration of 0.068 ppm. In terms of air quality, the worst situation was experienced in 2011, which about 31 percent of the days have been marked as unhealthy, but during the last years of the study, the air quality get better.

Conclusion: In general, the results of the study showed that SO₂ concentration has been decreased during recent years due to strengthen of air pollution regulation but NO₂ concentration was increased because the number of gas fuel automobile was also increased. With regard to air quality, it has an improving trend during the study period.