Abstract: In this paper, FLAC3D is adopted to simulate the mechanical behavior and deformation characteristics with different excavating method and excavating sequence of large section cavern within soft rock. The research results have showed that the excavating process is a non linear irreversible process tightly related with stress paths and stress history.The non linear mechanics design method, which include mechanics countermeasure design, process optimization design, optimized parameter design,should be adopted in excavation plan design of large section cavern within soft rock.So the surrounding rock of cavern should be in stable state.