The accuracy assessment of air quality forecast in Guangdong province was discussed. Results showed that in case of not to distinguish the pollution levels, forecast accuracy of all cities in Guangdong Province are quite different. Forecast accuracy of Zhongshan was 92%. It was the only city whose accuracy was more than 90%. Yunfu ranked the lowest, with accuracy 53%. In case of distinguishing the pollution levels, in condition of measured air quality grade above light pollution, the accuracy was generally lower. Only the accuracy of Foshan, Dongguan and Guangzhou was more than 50%, while the accuracy of the other cities was 0. Considering the accuracy of different pollution levels, Foshan ranked first, ranking nine further than that in case of not distinguishing the pollution levels. Distinguishing pollution levels was more suitable for assessment of air quality grade forecast in Guangdong, where lighter air pollution takes place. In the case of ozone as the primary pollutant, the average forecast accuracy of Guangdong was lower than that in the case of other species as the primary pollutant.