Mobile passive differential optical absorption spectroscopy (DOAS) was used for the remote sensing of the emission flux of SO2 and NO2from area of a steel company during Beijing Olympic Games. The mean values of SO2and NO2flux were 4.1 ton/h and 1.0 ton/h derived from the observation results. The comparison of mobile passive DOAS results with MAX-DOAS observations shows a preferable identity and suggests that the results are reasonable and reliable. A further analysis revealed that the emission flux of these two gaseous pollutants decreased about 44% and 78% respectively. These results indicated that emission reduction had a remarkable effect.