ABSTRACT PM2.5 and ozone (O3) are two major pollutants worsening air quality in China. Taking Guangzhou as an example, we utilized the meteorological data from 4 weather stations and air quality data from 10 environmental monitoring stations during 2014-2016 to explore the variability of PM2.5 and maximum daily 8-hour average (MDA8) O3 concentrations in different ranges of major meteorological parameters. Critical values of individual meteorological parameters for the variability of pollutant concentrations were calculated. For PM2.5, the hourly concentration tended to increase when relative humidity > 50 %, hourly rainfall intensity ≤ 0.6 mm hour-1 or wind speed ≤ 1.8 m s-1, otherwise it tended to decrease. As for MDA8 O3, sunshine duration > 4 hours, the maximum temperature > 29 ℃ or daily average wind speed ≤ 1.8 m s-1 would tend to increase the concentration, while the opposite would decrease it. The wind direction is also an important meteorological parameter affecting pollutant concentrations. Under the control of the westerly wind, Guangzhou suffers from severe air pollution with a strong possibility. We used the critical values of these meteorological parameters as indicators to evaluate the favorability of meteorological conditions to air quality and found that the weather condition in 2014 was the most unfavorable in the past three years (2014-2016). This study gives a further understanding of the relationship between meteorological parameters and pollutant concentrations. The novel methods proposed in this study could be applied to guide air quality forecasts from a perspective of meteorological parameters, as well as compare the effect of weather conditions on air pollution for different years.