To investigate the changing regularity of the temperature field of a geogrid-reinforced soil (GRS) retaining wall under extreme temperature fluctuation, this study focused on a GRS retaining wall in a Urumqi engineering practice. Finite element models were constructed and employed to analyze the inner temperature distribution characteristics of the GRS retaining wall, taking into account the influence of solar radiation. The findings indicate a strong correlation between the inner temperature field of the GRS retaining wall and variations in environmental temperature, with the isotherm closely resembling a hyperbolic shape. Specifically, the field within approximately 3.0~4.0 m behind the facing panels and about 2.0 m below the top surface of the GRS retaining wall can be classified as a temperature-sensitive region. Furthermore, the width of this temperature-sensitive region expands in proportion to the thermophysical parameters. The utilization of filling materials possessing enhanced thermophysical properties can effectively alleviate the average temperature gradient; however, the magnitude of the average temperature gradient predominantly depends on the rate of fluctuation in the external temperature. The maximum depths of frost show an increase with the saturation of filling materials, with the most significant increment observed during the transition from a saturation level of 0 to 0.2.