Despite the extensive investigations to understand the difference between ground-based and space-borne measurements, there still exist differences in total ozone (TO) measured at those two different platforms. Comparisons were carried out for the first time between TO data obtaiend from the ground based Dobson and Brewer spectrophotometers, and the Ozone Monitoring Instrument (OMI) on board EOS-Aura satellite in a megacity site in Northeast Asia. The TO values retrieved by the OMI-DOAS (Differential optical absorption spectroscopy) algorithm tend to be lower than those measured by the ground based sensors in spring and summer as well as the low solar zenith angle condition. We found that such underestimation of the OMI-DOAS TO is caused by tropospheric ozone underestimated by the OMI-DOAS algorithm when tropospheric ozone are significantly enhanced.