Aiming at the problem of reasonable selection of coal pillar width in gob-side entry driving technology under the condition of secondary gob-side entry driving, taking the roadway layout and engineering geological conditions in Qianyingzi Mine as the background, theoretical analysis, numerical simulation and field engineering practice were adopted to study the gob-side entry. The theoretical width range of coal pillar is calculated by the limit equilibrium theory of coal pillar, and the distribution characteristics of surrounding rock stress and displacement of gob-side entry under the width of 4 m~8 m coal pillar are analyzed by numerical simulation. The research shows that the reasonable width of coal pillar is 4 m~8 m； under this geological condition; When the coal pillar size is 5 m~7 m, the stress of coal pillar is improved. It can ensure the stability of roadway while giving consideration to economic benefits to a great extent; Based on all the factors, it is determined that the reasonable coal pillar for gob-side entry driving in E3215 wind tunnel is 6 m. When the small coal pillar is supported by anchor and cable, the maximum deformation of the roof and floor and two sides of E3215 air roadway after delayed grouting is 154 mm and 196 mm respectively, and the overall deformation of the roadway is within the controllable range. The 6 m coal pillar and surrounding rock control technology of gob-side entry driving can realize the stability of double-lane coal pillar and long-term effective control of surrounding rock.