Abstract: An observational study on total ozone amount and its vertical profile is presented using the measurements taken in Lhasa in the summer of 1998. In combination with other data sets, it is proved that there is a natural "ozone valley" over the Tibetan Plateau. Analyses show that there are errors on total ozone amount between groundbased and satellite ozone measurements. Brewer Umkehr observations demonstrate that the layer with maximum amount of ozone in the stratosphere over Lhasa may exist in altitude ranging from 25 km to 27.5 km in summer, with higher values and narrower width when compared with other regions in the same latitude. But the Umkehr measurements overestimated the tropospheric ozone. Observations of ECC ozonesondes show that there has obvious lower amount of ozone in the troposphere over Lhasa in the summer season.