Abstract: This paper analyzes the radioactivity levels in the surface soil of 12 major cities in Inner Mongolia Autonomous Region from 2016 to 2023 (from the 13th Five-year Plan to the middle of the 14th Five-year Plan). The results show that there is no significant change of ²³⁸U, ²³²Th, ²²⁶Ra, ⁴⁰K radioactivity level in 12 major cities compared with the range of the survey results of the natural radioactivity level in the soil of Inner Mongolia Autonomous Region from 1983 to 1990, and no abnormalities were observed in the artificial radionuclide ¹³⁷Cs. Evaluation of γ radiation levels in 12 major urban environments were made by using external exposure index and equivalent radium concentration. The evaluation results showed that the external exposure index and the equivalent radium concentration in 12 major cities were within the allowable value range. The external exposure level of soil in the 12 major cities in Inner Mongolia Autonomous Region is in compliance with national regulation.

Key words: soil, radioactivity level, external exposure index, equivalent radium concentration, Inner Mongolia Autonomous Region