Abstract: The width of fractured zone of pillar is one of the major basis about design of stope stability in strip method mining.The strain energy balance theory is introduced，regarding as the strain energy among the strip ore layer composing of volumetric strain energy，shape strain energy and bending elastic energy.According to the elastic energy balance relationship before and after mining，the model for calculating the width of fractured zone of pillars is derived.The model is applied to calculate the width of fractured zone of two pillars in Shanghengshan ore-body，and the calculated results are compared with that of the similar simulation.The widths of fractured zone are calculated as 10.06 m and 12.42 m，respectively，which fit well with that of the similar simulation test.The influences of several possible factors to the width of fractured zone in the model are analyzed.The width of fractured zone of pillars has a positive correlation with the mine seam thickness，buried depth of ore-body and the volume-weight of overlying strata，and has an inverse correlation with the compression strength and Poisson's ratio of ore-body.Once the width of fractured zone increased，the width of strip mining increased firstly and then lowered.The research results can provide a certain theoretical guidance to the stability design of level and gently inclined strip pillar.

Key words: Strain energy balance, Strip pillars, Width of fractured zone