Abstract: This paper was based on the engineering research of 43^# coal seam working face of +640 level west-side in Wudong Coal Mine, analyzed fire traits and reasons in fully mechanized caving face which were induced by high temperature residual coals in the goaf on the top of extremely steep and thick coal seam, made fire prevention and extinguishing programs by nitrogen injection and applied, achieved that no fire happened in mechanized caving face in three years, provided reliable experiences for fire prevention and extinguishing under similar conditions.