Conventional equivalent continuum theory poorly interprets the bending deformations and damage phenomena encountered in rock engineering because the theory ignores the influence of gradient stress.The influence of the bending effect on deformation characteristics of the media has been considered in Cosserat continuum theory which introduces the concepts of coupled stress and bending curvature.The basic principle of Cosserat medium theory and its expanded constitutive model were introduced firstly.Next,a numerical simulation of an underground cavern was carried out using FLAC software.After this,the results of the Cosserat model and explicit joint model were compared.The simulation results not only displayed the bending deformation of layered rock mass well,but also demonstrated the validity and superiority of the Cosserat expanded model.