Abstract: The effect of the ratio of vertical stress and horizontal stress and the effect of Taxonomic covariance of the size and parameters of rock structure (the ratio of span and the height of laneway) on wall rock stability were researched using the method of FLAC numerical simulation based on Fushun-west-open pit . The result shows that: there is self-balancing arch in the excavation disturbing zone of roadway surrounding rock. The feature of it is made up of higher stress binds than else zones in surrounding rock. The self-balancing arch which bears and passes load of overlying strata is primary supporting body .The shape of self-balancing arch is affected by stress circumstance and the size and parameters of laneway.