Abstract: The radioactive anomalies of coal-bearing series from some coalfields in Liaoning Province are found through a second interpretation of natural gamma-ray logging data of boreholes. Among the 3437 screened boreholes, 841 are discovered with anomalies, including 49 related to coal seams with abnormal values of 50-123 γ and individual peak value up to 260γ. The raw coal and ash samples collected from five coal mines are analyzed to determine the post-combustion migration ratios of ²³⁸U, ²³²Th, ²²⁶Ra, ⁴⁰K, ²¹⁰Pb and ²¹⁰Po and their influencing factors. The results show that the coal/ash activity ratios and ash rates of the former five elements are similar, indicating no volatilization or chemical reaction occurred during the combustion process, and almost all the element contents are concentrated in ash;while those of the element ²¹⁰Po is quite different for it is easily transported into air in the form of gas in coal burning. Therefore, it is necessary to pay attention to the radioactive anomalies of coal-bearing formations directly related to coal mining and utilization to avoid their pollution on environment.