In order to improve the resource recovery rate, technology small coal pillars of gob-side entry was used in the return wind groove of No.15203 Face of Zuoquan Hongyuan Coal Industry. Through theoretical calculation and numerical simulation, the range of stress reduction zone after mining in the upper section of working face was mutually verified, and the width of coal pillar should not be more than 10 m. The numerical simulation and comparison of the plastic zone range and stress distribution of surrounding rock under different width coal pillar conditions were carried out. It was found that the vertical stress in the coal pillar with 6 ~ 8 m or 20 m width was lower than that in the coal pillar with 8 ~ 20 m width, and the plastic zone in the coal pillar with 6 ~ 8 m width was not completely connected. Combined with the actual production conditions, the width of the coal pillar was finally determined to be 7 m. Roadway support was anchor cable + bolt with metal mesh protection table. The cumulative deformation of coal pillar side was 288 mm, the cumulative deformation of coal mining side was 179 mm, the cumulative subsidence of roof was 168 mm, and the cumulative amount of floor heave was 676 mm.