Abstract: Permanent pillars are often required to ensure the stability of surface structures when mined shallow deposit, design the reasonable width of pillar is important on the premise of pillar safety.The Hoek- Brown strength criterion and the pillar area bearing theory were used to derive the expression of the pillar safety factor based on an iron mine.The authors analyze the sensitivity of influencing factors through the orthogonal test, and study the quantitative relationship between the safety factors of the pillar and the main influencing factors.The results show that the great significant factor is mining depth, horizontal stress of filling, room width and pillar width, the safety factors of the pillar’s relationship between influencing factors are exponential decrement, exponential increment, polynomial decrement and polynomial increment, respectively.The reliability has confirmed when room is 40 m wide and pillar width is calculated is 9 m based on numerical simulation.