Abstract: Based on the situation of waste of resources and strong rock pressure which cause by unreasonable coal pillar width during the process of mining, borehole stress and PASAT CT scanning technology are used to evaluate the rationality of existing coal pillar size, and then the theoretical calculation and numerical simulation are used to optimize the section coal pillar. The results show that elastic core of 6 m is the main reason to cause strong rock pressure and the existing size of section coal pillar of 30 m is slightly big; the narrow coal pillar size after optimization is 8 m, which makes the coal pillar in elastic-plastic critical state, and the stress level of coal pillar is at reasonable level.