Abstract: Mercury release behavior and speciation during pyrolysis of Datong and Baorixile coals were studied in a temperatureprogrammed tube furnace under N₂ atmosphere. The results showed that mercury emission from coal pyrolysis significantly depended on temperature. The release ratio of Hg in coal increased dramatically with increasing temperatures, and more than 92% mercury was released at 600℃. Elemental mercury was the dominant species in the gaseous mercury during coal pyrolysis. The percentage of Hg⁰ of Datong coal increased firstly, and then decreased, while it reduced gradually for Baorixile coal. Both the rate of Hg release and the percentage of Hg⁰ rose finitely through the time ranging from 0~60min, and Baorixile coal displayed more significant increase than Datong coal. Higher heating rate promoted the mercury release in coal and enhanced the proportion of Hg²⁺ in gas; especially for Baorixile coal it reached 19.5%, being apparently higher than that for Datong coal.