Based on the O₃ and meteorological data observed in northern suburb of Nanjing in 2008, the time series and the variation characteristics of the daily averaged O₃ was analyzed with a Matlab wavelet method, the results indicated that the O₃ concentration in spring and summer were higher than that in autumn and winter . And the daily maximum and minimum values were presented in late spring to early summer and winter respectively. There were five O₃ concentration mutation points during the whole year.. The mutational variation of the O₃ concentration was caused by the high-pressure system, high temperature, low humidity and the sunny and cloudless climate. The source of the pollutants was studied with a HYSPLIT-4 pollutant dispersion model, the results showed that the pollution source leaded to the higher level of O₃ concentration was mostly come form the local pollutant and transportation of outer pollutant, the transportation of the O₃ in regional scale or mesoscale was mainly stabilized at the bottom of mixing layer in the vertical direction.