Abstract: To investigate the regulations of ozone concentration change,we have used monitoring data of ozone in the 16 cities of Yunnan in 2015.The results show that the fine rate of air quality in Yunnan Province reached 98.9%,and the whole air quality maintained a good condition.Ozone as the primary pollutant days accounted for 46.3% of the whole polluted days.The highest ozone concentration appeared in May,followed by March and April.Ozone concentration changes have a significant effect on the weekends.Ozone concentration over the weekend is higher than that the working day except in Jinghong and Dali.The average concentration of O3-8h in one day showed an unimodal curve, with the minimum value appeared at 8:00—9:00 and the maximum value appeared at 16:00—17:00.