In order to explore the release and capture laws of fluorine in coal during oxygen bomb combustion, the key factors that lead tothe low determination results of high-ash and high-fluorine samples were revealed. Selecting coal samples with different ash and fluorine contents as the research object, the the influence of coal quality characteristics on the maximum flame temperature and the vapor/ fluorine ratio at this temperature in the oxygen bomb was analyzed by using the thermodynamic state function method. The effect on the releaseand capture rate of fluorine was also analyzed. The results show that the maximum flame temperature and the vapor/ fluorine ratio ofthe combustion environment is directly affected by the calorific value of the sample, and the effective heat obtained in the fluorine decomposition process is the key factor affecting the release and capture of fluorine. The release and capture rate of fluorine in high-ash andhigh-fluorine samples can be improved by adding benzoic acid to increase the calorific value and reduce the fluorine content of the sample.The fluorine release and capture rate of high-ash and high-fluorine samples can be increased from 52%-70% to 85%-100% by raisingthe theoretical maximum temperature to 2 800 K, achieving the full release and capture of fluorine. This study can provide a basis for expanding the scope of application of oxygen bomb combustion method to determine fluorine content, and also provide a basis for fluorine fixation in the application of high fluorine coal.