Abstract: Adopting some reasonable structural parameters for stope is a key measure to control ground pressure and achieve the safe and efficient exploitation of ores.In view of iron rock conditions of Wuzhuang iron mine，FLAC3D three-dimensional finite difference analysis software is used to calculate the surrounding rock stress，the displacement variation rules and the distribution of plastic zones of 24 different programs，obtaining that tensile stress of mine stope roof is the key factor of affecting the mine stability.Taking the maximum tensile stress suffered by the roof strata as an indicator index of measuring the stability of stope plots，the relationship curve of between the stope span and tensile stress，and the stope length and tensile stress，and the joint impact curve of both parts and the tensile stress are drawn.Under circumstances of a certain roof thickness，the tensile stress of the stope roof increased with stope span increased and this increase will be higher and higher; With the stope length increase，the tensile stress of the roof increased a little，especially when the stope length increased to a certain length，the roof tensile stress can keep stable.Now a conclusion comes: the stability of stope not only has a relationship with the size of the exposed roof，but the exposed surface shape has a crucial influence on its stability.The roof shape optimization is one of the important means to control the ground pressure.A long strip of exposed roof surface shape can improve productivity of the stope and ensure mining safety.Therefore，the “broader stope area，smaller stope span” design philosophy for the mine are proposed.

Key words: Displacement variation rule, Plastic zone, Roof tensile stress, Exposed surface shape