Mechanical properties of Coal Seam No.13 in Jianxin Colliery are tested by using Rock Servo Mechanics Test System. The coal masses unaxial compressive strength is tested to be 6.928 MPa through size effect study. And the coal is testified to accord with Mohr-Coulomb elastoplastic model by triaxial compression test. Based on the experimental study

the pillar stress and maximum subsidence are studied by using FLAC3D; and the pillar security is analyzed after selecting the mining strip width of 25 m

then the stability of coal pillar is studied. The results indicate that the width of 20 m can maintain pillar stability. On the basis of coal test in laboratory with numerical simulation method

studying strip pillars’ stability of different widths can insure its stability and safety while reducing the size of pillar

then avoiding blindness by using empirical formula merely.