The ground surface NO2 concentration (cNO2) and tropospheric NO2 vertical column density (NO2 VCDtrop) in Shanghai area were measured by ground-based active and passive DOAS methods from May 2015 to May 2016. The hourly cNO2 measured by LP-DOAS was positively associated with Air Quality monitoring data (r=0.81), while the NO2 VCDtrop retrieved form MAX-DOAS measurements agreed well with GOME-2 and OMI satellite observations (r=0.89, 0.88). The results of both active and passive DOAS were reliable. In daytime, Mixing Layer takes up a majority of Planetary Boundary Layer, where most of the air pollutants’ transportation, dispersion, dilution and deposition occur. The concentration of pollutants such as NO2 mixes well within the Mixing Layer and reduces nearly to zero in free troposphere above the Mixing Layer. A new method was proposed to estimate the Mixing Layer Height (MLH) by combining the active and passive DOAS observations. The feasibility of this method was discussed in details in this paper. The calculated MLH was significantly correlated to Planet Boundary Layer Height (PBLH) deduced from GDAS meteorology database (r=0.93). Both MLH and PBLH ranged from 0.1 to 2 km. The diurnal variation showed a single peak. The MLH reached the maximum during 12:00 to 15:00, whereas the PBLH peaked at 14:00 due to the lower temporal resolution. The monthly averaged MLH and PBLH had similar seasonal variation, which were higher in Sept. 2015 and Feb. 2016, and lower in July 2015 and March 2016. The ratio of MLH and PBLH was 0.98±0.59, which was consisted with the relationship between them. The deduced MLH was also highly correlated with PBLHLidar obtained from the co-located Lidar results (r=0.75). PBLHLidar value was slightly higher than MLH, but they tended to be the same at the beginning and end of daytime. The validations with other methodologies suggested that this method was evidently reliable.