This study analyzed the spatio-temporal variability of air quality data for six standard air pollutants (Particulate Matter 2.5 (PM_2.5), Particulate Matter 10 (PM₁₀), SO₂, NO₂, CO, and O₃) in the Sichuan Basin (SCB), China from 2015 to 2018 in relation to the formation of haze using conventional meteorological data (temperature, wind speed, and relative humidity), satellite data (fire point data, vertical profiles of aerosol subtypes, and aerosol optical depth), planetary boundary layer height, and backward trajectories. The results indicated that the spatio-temporal evolution of the air quality index (AQI) had notable seasonality for the pollution severity in descending order: winter, spring, summer, and autumn. Autumn and winter severe haze events occurred in November and January, respectively, and were caused by higher local pollution emissions under stagnant air conditions. Spring severe haze events occurred in May and were caused by dust from Northwest China and local regions. Severe summer haze events occurred in July and were caused by local burning. Therefore, the analyses showed that local burning, stagnant meteorological conditions, air mass transport and anthropogenic pollution emissions played a key role in haze in the SCB. This study provides scientific insights for fully analyzing heavy air pollution in SCB, China, and also provides a scientific basis for pollution research in regions of complex terrain as basins and mountains.