In this paper,the in-situ pyrolysis process of coal mass is analyzed based on multi fields coupling theory.It is found that the in-situ pyrolysis process is essentially a coupling process of pyrolysis and seepage.Based on this result,a mathematical model for the coupling process of in-situ pyrolysis and seepage of coal mass is brought out.The research provides a base for the in-situ gasification and liquefaction mining of coal in future.