Abstract: The soil thermal conductive equation and that with thermal convection term contained were solved analytically. Based on the observation data from soil moisture and temperature measurement system(SMTMS) sites during GAME/Tibet over Tibetan Plateau in September 4-10, 1998, we calculate the apparent soil thermal diffusivity by harmonic method (HM) and Laplace transform method (LTM), and the soil thermal diffusivity by the analytical resolution to soil thermal conductive equation with thermal convection term contained. This study demonstrates that the apparent soil thermal diffusivity in this area over the Tibetan Plateau is between 0.30×10-6 and 0.98×10-6m2/s in the upper layer(at depths 0.04 m to 0.20 m) where the soil thermal diffusivity should be between 0.15×10-6 and 0.72×10-6m2/s. Harmonic method(HM) leads to somewhat greater values of the apparent soil thermal diffusivity than the LTM method, furthermore, apparent soil thermal diffusivity is greater than soil thermal diffusivity.