Abstract: Based on the thermal equilibrium theory and temperature distributing formula of semi-infinite region and numerical simulation method, the authors study the change regularity of the buried pipeline temperature field influenced by the unsteady environment temperature. The mathematical model is completely considered the influence of the physical property change of soil impacted by the unsteady environment temperature upon the buried pipeline temperature. And it is transformed the semi-infinite region into the finite region contemporary, which enhances the computing speed and the definition of the result. Compared with actual test data, the mathematical model is exact to some extent, and with high precision.