Abstract: To study the influence of continuous open nitrogen injection on distribution characteristics of spontaneous combustion “three zones” in the goaf, this paper takes 902 working face of Daxing Coal Mine as the research object, and carries out the simulation experiments of coal spontaneous combustion under different O2 concentrations (20.9%, 10.0% and 7.0%), and analyzes the relationship between CO gas products and coal temperature, obtains that the critical oxygen concentration of No. 9 coal seam in the study area is considered to be 7%. Based on the field measurement of CO and O2 concentrations at different positions in the goaf under different nitrogen injection rates by beam pipes arranged in 902 return air lane, it is concluded that nitrogen injection rates are negatively correlated with the width of the oxidation zone, and nitrogen injection rates do not affect the characteristics of the distribution zone. Combined with the final determination of the average thrust of the working face, 1 200 m3/h stepped buried pipe and continuous open nitrogen injection method for fire prevention and extinguishing can meet the daily fire protection needs of 902 working face.