Abstract: In order to understand the distribution range of high gas concentration in the Y ventilated goaf,a three-di- mensional measurement device for the regional distribution of gas concentration in goaf has been inde-pendently devel- oped. The device is mainly composed of gas recovery head,gas collector,gas flow monitoring device,gas gathering de- vice and gas concentration detector. It can be used to obtain the three dimensional meas-urement of gas concentration in different space areas of the goaf. The device was successfully applied to the mine site to measure the spatial distribu- tion of gas in the goaf near gob-side entry retaining. The field test results show that under the Y ventilated goaf of sub- level gob-side entry retaining,there is a gas agglomeration in a certain space range in the goaf near the gob-side entry retaining. The space range of gas agglomeration is away from the gob-side entry retaining 30-45 m along the working face,away from the working face 35-55 m along the gob-side entry retaining,and away from coal seam floor 15-30 m along the direction of vertical coal seam floor. The highest gas concentration is up to 0. 9% . Under different working conditions,the space range of high gas concentration in the goaf is basically the same. The high gas concentration zone formed by the goaf near the gob-side entry retaining has a serious threat of gas explosion. Therefore,it is necessary to take effective measures to strengthen the monitoring and control of the high gas concentration area in the goaf near the gob-side entry retaining.