Abstract: In order to improve the stability of coal pillar and surrounding rock on gob-side roadway in isolated fully mechanized working face of ultra-thick coal seam, taking the isolated fully mechanized working face of 61102 ultra-thick coal seam in Tangjiahui Coal Mine as the background, by means of theoretical analysis, numerical simulation and field measurement, the reasonable size of coal pillar and roadway support method on gob-side roadway were studied in the isolated fully mechanized working face of ultra-thick coal seam. The results show that by using the stress limit equilibrium theory, the distribution law of internal stress field and finite element method to compare the plastic zone and stress distribution characteristics of different coal pillar widths, it is concluded that the width of coal pillar on gob-side roadway in the isolated fully mechanized working face is 21 m; the combined support method of "anchor net cable" + "reinforced ladder beam" + "steel strip" can effectively reduce the migration of surrounding rock on gob-side roadway, and significantly improve the overall stability of surrounding rock. The research results can provide reference for mines under similar geological production conditions.