Based on average daily PM10 concentrations and meteorological data of Nanjing in 2005, we conclude the change rules of PM10 concentrations by using Matlab wavelet tool, which shows that PM10 concentrations are relatively higher from Feb. to May, from Oct. to Dec. and lower from Jun. to Sep., and find five break points in 2005. Then we trace the source of pollutant by integrating the HYSPLIT-4 pollutant dispersion model. It indicates that emission of local pollutant and transportation of outer pollutant cause the atmospheric pollutant in Nanjing, as for the vertical direction, long-distance transportation of pollutant is always restricted to the bottom layer.