Analysis of total ozone data measured at Taipei and Chengkung in Tqiwan, suggests that the spatial variation of column ozone over Taiwan is negligible. Further analysis of the ozone sounding data over Taipei indicates that the seasonal variation of total ozone is strongly correlated to the change of stratospheric ozone and has a typical pattern of spring maximum and winter minimum. The tropospheric ozone occupies about 16% of the total column ozone, and has maximum levels in spring and summer. Intrusions of stratospheric ozone and meridional ozone transport by the Hadley circulation have resulted in higher ozone levels in the upper and mid-troposphere in spring. Photochemical ozone production in the boundary layer is crucial to the summer maximum. Column ozone below 2km height occupies about 3% of the total column and 18.6% of the troposphere ozone, which can be enhanced to 36% in July. Comparing this study's data with estimates from satellite data by Fishman et al. (1990), we note that there were changes of -3.3%, -8.2% and 34% in the total, stratospheric and tropospheric ozone, respectively, from 1979~1987 to 1994~1999. The tropospheric ozone-increasing trend is most noteworthy.