[Objective] The evolution of drought frequency and intensity was demonstrated yearly and quarterly in Chongqing City to provide scientific basis and reference for drought mitigation. [Methods] Standardized precipitation index(SPI) drought index method was used, and the monthly precipitation data collected from 34 meteorological stations in 1964-2011 were dealt. [Results] Frequency of drought had obvious regional and seasonal traits. The seasonal frequency of droughts varied differently. In spring, summer and winter, it had a range of 25.9%~35.1%; In fall, it had a big range from 16.7% to 40.0%. Either for yearly drought intensity or seasonal intensity, they both had an overall increasing trend, among which, annual drought intensity and the autumn one were more obvious. In the past 50 years, the study area was prevailed by intensity grades of mild drought and drought, either counted by years or by seasons. Drought occurred in summer and autumn were more severe than that in other seasons and in a whole year. [Conclusion] Standardized precipitation index(SPI) can be used as indicators for monitoring the climate change of Chongqing City. The frequency of drought in Chongqing City has obvious regional and seasonal traits.