Abstract: By combining thermogravimetric (TG) and mercury analyzer analysis 5 different rank coal's oxidation pyrolysis, the different rank coal's pyrolysis and mercury release behavior was studied. The results show that the XRD characteristics diffraction peaks can show coalification degree, the higher diffraction peak intensity and the narrower the peak width, the higher coalification degree is. Different coalification degree's coal burning in oxygen, the mass losses increased with metamorphic grade, and with the increase of coalification degree, combustion oxidation onset temperature, the maximum thermal decomposition temperature and the final temperature gradually increased. With the increase of coal metamorphism, the release time of mercury in coal gradually extended, and the maximum mercury release rate corresponding to the maximum mass loss temperature increased.