In order for current laboratory studies of strata performances under high temperature to be applied in Underground Coal Gasification (UCG) technology, the temperature scope (range) of UCG must be studied. Based on the heat conduction differential equation, this paper simulates the transverse section temperature distribution of UCG in the multi-physics coupling field. It demonstrates that the strata properties at a range of two meters are affected by high temperature, and the influence on sandstone is more obvious than that of coal. The temperature curves show a trend of linear to nonlinear as time goes. This paper presents the precedent of using multi-field coupling calculation to simulate UCG.