Abstract: In the conventional SF6 micro-water test, it is often necessary to measure the dew point temperature first, and then obtain the micro-water value by looking up the table according to the dew point temperature. When there is a lot of data to be processed, the workload will be significantly increased. In order to reduce the workload when there are a lot of data, this paper uses the cftool curve fitting tool in MATLAB to process the data in the corresponding table of SF6 micro-water dew point, puts forward the empirical formula of micro-water and dew point within the range of -60℃,0℃, and uses MATLAB programming to calculate. It is proved that the empirical formula is accurate in the interval of -60℃,0℃.