Daily meteorological observation data of 17 stations of Chongqing and NCEP/NCAR reanalysis data are employed to diagnose the influence of urbanization on the summer high temperature and sultry weather in Chongqing. Results show that high temperature days and hot days at Shapingba Station decrease with the rapidly accelerating of urbanization. Maximum temperature decrease is the main reason for the decrease of high temperature days and hot days. Correlation analysis indicates that the difference of hot days between the main urban zone and suburbs increases gradually,which indicates the decrease of high temperature days and hot days at Shapingba Station is caused by the rapidly accelerating of urbanization,not by the regional climate changes. Observation Minus Reanalysis (OMR) method is used to analyze the difference between observed temperature and NCEP/NCAR reanalysis (NNR) temperature. So, we found that along with the rapidly accelerating of urbanization, mean temperature and minimum temperature increase, especially for minimum temperature, but maximum temperature decreases.