Abstract: Anewmet hod is designed to calculate the strength index (IS),the western limitindex (IW) and the northern limitindex (IN) of Subtropical High (STH) with the 500 hPa geopotential heightset.Based on this statistical method,three ST Hindices of 12 months are reconstructed back to year 1880 using reconst ructed 500hPa geopotential height set from 1880 to 1950.Then the 120 year sets of the STH indices are got with the observed 1950 1999 ST Hindices provided by NCC1.It forms a 12 month series from 1880 to 1999.Then,power spectra and wavelet transformation are made to analyze the annual and interannual variation of IS,IW and IN during 1880 and 1999.