<p>In recent years, satellite remote sensing has been increasingly used in the long-term observation of ozone (O<sub>3</sub>) precursors and its formation regime. In this work, formaldehyde (HCHO) data from Ozone Monitoring Instrument (OMI) were used to analyse the temporal and spatial distribution of HCHO vertical column densities (VCDs) in Shanghai from 2010 to 2019. HCHO VCDs exhibited the highest value in summer and the lowest in winter, the high-VCD concentrated in western Shanghai. Temperature largely influence HCHO by affecting the biogenic emissions and photochemical reactions, and industry was the major anthropogenic source. The satellite observed formaldehyde to nitrogen dioxide ratio (FNR<sub>SAT</sub>) reflects that the O<sub>3</sub> formation regime had significant seasonal characteristics and gradually manifested as transitional ozone formation regime dominated in Shanghai. The uneven distribution in space was mainly reflected as the higher FNR<sub>SAT</sub> and surface O<sub>3</sub> concentration in rural area. To compensate the shortcoming of FNR<sub>SAT</sub> that it can only characterize O<sub>3</sub> formation around satellite overpass time, correction of FNR<sub>SAT</sub> was implemented with hourly surface FNR and O<sub>3</sub> data. After correction, O<sub>3</sub> formation regime showed the trend moving towards VOC-limited in both time and space, and regime indicated by FNR<sub>SAT</sub> can better reflect O<sub>3</sub> formation for a day. This study can help us better understand HCHO characteristics and O<sub>3</sub> formation regime in Shanghai, and also provide a method to improve FNR<sub>SAT</sub> for characterizing O<sub>3</sub> formation in a day, which will be significant for developing O<sub>3</sub> prevention and control strategies.</p>