Abstract: By Analyzing the observation data of Yuanjiang water radon,we found it has a very good corresponding relationship before the earthquake of south Yunnan and southwest Yunnan,and it is a sensitive material before the earthquake in south Yunnan and southwest Yunnan.It`s earthquake reflecting characteristics is:when the day average appears anomaly sudden jump in groups,and five day average more than 1 times average variance line for a long time,and accompanied macroscopic phenomena at the wellhead such as inverted flower bubbling and flow rate increases.When the wellhead appears macroscopic phenomena,there will be at least two ML5 or one ML6 earthquake generally.