In order to analyze the reasonable width of narrow pillar in isolated island working face, combined with the engineering example of 2102 island working face in a mine, the cusp mutation model is introduced to theoretically analyze the reasonable width range of coal pillar.FLAC^3D numerical model is established to simulate the vertical stress distribution and the plastic zone distribution of roadway surrounding rock under different coal pillar widths.The theoretical calculation results show that the limit width of coal pillar should be wider than 7.5 m according to the cusp mutation model.The numerical simulation results show that when the width of coal pillar is 6-8 m, the surrounding rock of the whole mining roadway is in a low stress environment.When the width of the coal pillar is wider than 8 m, the concentrated stress begins to appear inside the coal pillar, and with the increase of the width of the coal pillar, the degree of concentrated stress is more obvious.Finally, it is determined that the width of the narrow coal pillar of the 2102 isolated island working face is 8 m.Site layout of mine pressure measuring station monitoring roadway surface displacement and roof separation, no obvious deformation of roadway surface, the maximum amount of floor heave 280 mm, two-sided displacement within 130 mm, roof subsidence within 50 mm.The roof abscission layer amount is small, the shallow separation amount is within 5 mm, and the deep separation amount is within 3 mm, which can ensure the safe mining of the working face.