Abstract:From September to November of 2014, we laid out four deep geothermal stations near the Sichuan-Yunnan fault zones (Binchuan, Lijiang, Tengchong and Wulong). The results show that the annual cycle effect of solar radiation decreases with the increase of underground depth, and the influence of the annual activity of solar radiation basically disappears at 14m and there is a difference with theoretical calculation, which may be related to the characteristics of underground media and widely developed hot springs in Sichuan-Yunnan region. The peak of solar radiation decays exponentially with depth, and the trough increases logarithmically with depth. At the depth of 14 m, the tidal wave valley of the solar radiation basically disappears. The thermal diffusivity of different depths is retrieved by Newton iteration, and the results show that the thermal diffusivities increase with depth in Binchuan, Lijiang and Tengchong, and the thermal diffusivity of Wulong increases with depths below 4 meters. Although the range of variation is different, it basically assumes exponential function.