First,by using iterative EOFs expansion,the data of soil temperatures in 0.8m and in 1.6m are,retrieved,then the persistence and the characteristics of oscillation are studied.Results show that:there are durations of 3-5 months on soil temperature in 0.8 m and about 6 months in 1.6 m,significant periodic oscillations of about 12 months which attribute 24.4% and 32% to total variance on soil temperatures in 0.8m and 1.6m respectively.The spectral variance of longer periodic oscillation is higher in 1.6m than that in 0.8m.But the spectral variance of shorter periodic oscillation is lower in 1.6 m than that in 0.8 m.