The “Sixstep” method of air quality forecast in the Pearl River Delta (PRD) region was introduced and the accuracy of air quality grade and primary air pollutant forecast in 2015 were analyzed. The results showed that the air quality in the PRD region in 2015 was quite good. The accuracy rate of 24 hour air quality grade forecast was highest in January while lowest in February， with annual average of 87.6%. Primary air pollutants included PM_2.5，PM₁₀，O₃-8 h and NO₂.The accuracy rate of primary air pollutant forecast was highest in September while lowest in March，with annual average of 72.7%.