Abstract: The coal pillar width is the main parameter of gob-side entry driving technology, which plays a key role in the success of roadway retention. The stability of the coal pillar can be described by the features of the neutral zone of the horizontal deformation of the coal pillar. The size of the neutral zone and the change of the bearing capacity can characterize the stability of the coal pillar. Based on the typical engineering background and the neutral zone theory of the coal pillars of roadway protection, a numerical model was established to simulate and analyze the change characteristics of the shape of the neutral zone and the bearing capacity in the coal pillars with different widths; as the width of the coal pillars increases, the width of the neutral zone in the coal pillars gradually increases, and the bearing capacity of the coal pillars also gradually increases, but the proportion of the neutral zone width first increases, then decreases and then increases. The increase rate of the coal pillar bearing capacity first increases and then decreases. The coal pillar could keep stability when the width is 6-7 m. The comprehensive theoretical calculation, numerical simulation results and field conditions determine that the reasonable width of the coal pillar is 6 m.