Abstract: The width of the sectional coal pillar would be an important factor affected to the surrounding stability of the mining gateway.The width of the sectional C oal pillar in coal mining face of Pingshuo No.3 Underground Mine is an experienced value of 20 m.In order to optimize the width of the sectional coal pillar and to impro ve the resources recovery rate,a site measurement,theoretical calculation and numerical simulation method were applied to study the width of the rational sectional coal pillar in Pingshuo No.3 Underground Mine.The stress measurement of the coal pllars showed that the 20 m width coal pillar between No.9104 coal mining face and No. 9105 coal mining face in No.3 Underground Mine could have certain surplus . According to the ultimate balanced theoretical calculation and the numerical simulation res ults,the rational width of the sectional coal pllar in Pingshuo No.3 Underground Mine should be over 12 m.