The present invention relates to a gas distribution detection method in a coal mine underground goaf. According to the present invention, the method is the streamline method, which adopts in situ direct sampling, transmission, collection and storage, detection, calculation, analysis and comparison according to the condition of the coal mine underground goaf to carry out the detection; a computer technology and sensors are adopted for collecting data of the gas; microcomputer programs are adopted for completing various analysis functions; the detection method adopts in situ direct sampling in the goaf, transmission, analysis, data printing, such that the process is rapid, the data is abundant and accurate, the gas distribution condition of the goaf can be directly mastered so as to provide the firsthand field data for treatment and elimination of the gas hazard; the detection method is rigorous, advanced, in site, intuitive, convenient, accurate and safe, and is an ideal gas distribution detection method in the coal mine underground goaf.