Abstract:A new intelligent back analysis method based on excavation damage zone(EDZ) thickness,increment displacement of rock mass and evolutional artificial neural network is presented for understanding the particular mechanical activity of rock mass under high earth stress and for estimating surrounding rock stability of deep underground rock engineering. The method is applied to stability analysis for the large caverns of Laxiwa Hydropower Station,which is the largest underground caverns located on the Yellow River. Through getting key rock mechanical parameters by sensitivity analysis and building the united sufficiency function based on the increment displacement and EDZ thickness,the rational values of five key rock mechanical parameters are recognized using the method. The results of qualitative analysis of EDZ and time serial displacement grey correlation analysis indicate that the method is credible.