Using the climate diagnosis method of wavelet analysis, power spectrum analysis and climate trend coefficient, and climate tendency rate, the climate change law and periodic characteristics of high temperature of the southern Jiangsu Province in 65 years are analyzed from the aspects of the number of high temperature days, annual average maximum temperature, and annual extreme maximum temperature by taking Changzhou as an example. The results show that there are decadal fluctuation characteristics in the number of hightempera〖JP2〗ture days, a downtrend from 1950s to 1980s， but a rising trend after the 1980’s. 〖JP〗There was a very significant difference in the number of high temperature days between 2000s and 1980s and significant difference between 2000s and 1970s. The average maximum temperature experienced several decadal change stages, including warming, cooling, slow warming, rapid warming and so on, but the overall trend was warming. The decadal variation of the number of hightemperature days was remarkable; the difference between maximum and minimum was 48 For the number of annual high temperature days, the annual average maximum temperature, and the annual extreme maximum temperature, the climate trend coefficient and climate tendency rate were greater than 0 There was 15year cycle characteristic in annual average maximum temperature.