To address the problems of resource waste and roadway instability caused by unreasonable coal pillar retention during gob-side entry driving in isolated island working faces, No.8102 isolated island working face of Tongxin Mine was adopted as the research object. Theoretical calculation, FLAC3D numerical simulation and field monitoring were combined to analyze the stress distribution and surrounding rock deformation characteristics under coal pillar widths of 5 m, 6 m, 7 m and 8 m. Three groups of monitoring stations were arranged in different sections on site, and displacement monitoring was carried out. The results showed that positive correlations were presented between coal pillar width and stress concentration degree, as well as vertical/horizontal stress peak values. The deformation of roof-floor and coal ribs was gradually reduced and mitigated with the increase of coal pillar width. Based on theoretical analysis and simulation results, the optimal retained width of coal pillar was determined to be 6 m, which could effectively avoid the bearing failure of narrow coal pillars and excessive stress concentration of wide coal pillars. It was verified by field monitoring data that the surrounding rock displacement of the driving roadway under this coal pillar width was all controlled within the engineering allowable range. The research results could provide engineering references for coal pillar retention in similar working faces.