There have been a lot of researches on urban ash haze pollution and its formation mechanism. But after the ash haze, it has not been paid enough attention by the researchers whether the ash haze pollution could initiate the photochemical pollution in the situation in which the air pollution degree has not declined. This article takes Pearl River Delta as a study object, and focus on the possibility of the photochemical pollution occurrence and the degree of the photochemical pollution after the city ash haze pollution occurrence. On the basis of the remote sensing software ENVI, geographic information system software ArcGIS and the statistical analysis software SPSS, it adopts the comparative analysis methodology which integrate the satellite remote sensing data with the ground monitoring data to observe the value change of ozone when the ash haze dissipation sunlight is still intense. It uses the 2007 data to carry on the foundation analysis, and conducts the confirmation research in 2008 to realizes the monitor and the forecast on ash haze-caused photochemical pollution. The result indicated that: When ash haze evanesces and the sunlight is intense, the contamination still exists. If the sun radiates, the possibility of photochemical pollution increases and the pollution degree enlarges. On this basis, we can make forecasts and early warnings of the photochemical pollution and its degree, and propose the corresponding prevention and the controlling measures to reduce the air pollution damages.