We performed MAX-DOAS measurements during the PRIDE-PRD2006 campaign in the Pearl River Delta region (PRD), China, for 4 weeks in July 2006 at a site located 60 km north of Guangzhou. The vertical distributions of NO<sub>2</sub>, HCHO, and CHOCHO were independently retrieved by an automated iteration method. The MAX-DOAS measured NO<sub>2</sub> mixing ratios showed reasonable agreement with the simultaneous, ground based in-situ data. While the tropospheric NO<sub>2</sub> vertical column densities (VCDs) observed by OMI on board EOS-Aura satellite agreed with those by MAX-DOAS, the 3-D chemical transport model CMAQ overestimated the NO<sub>2</sub> VCDs as well as the surface concentrations by about 40%. From this observation, a reduction of NO<sub>X</sub> emission strength in CMAQ seems to be necessary in order to well reproduce the NO<sub>2</sub> observations. The average mixing ratios of HCHO and CHOCHO were 12 ppb and 1.6 ppb, respectively, substantially higher than in other rural or semirural environments. The high ratio of 0.135 between CHOCHO and HCHO corresponds to the high VOCs reactivity and high HO<sub>X</sub> turnover rate consistent with other observations during the campaign.