Abstract: In order to study the mechanical mechanism of chamber surrounding rock in the process of excavation-sup- porting,the circular chamber was divided into elastic zone,plastic softening zone and plastic residual zone in accord- ance with mechanical characteristics of surrounding rock. The surrounding rock softening,dilatation,spatial effect and anchorage mechanical effect were considered and the softening modulus of strength parameters,coefficients of dilatancy and dilatation angle were introduced. The analytical solutions of elastoplastic stress,displacement and plastic zone radi- us were obtained. In addition,an example was analyzed to study the effect of different factors on the stress of plastic zone,surrounding displacement and plastic zone radius of chamber. The results show that anchorage mechanical effect can decrease plastic range and plastic zone radius for the large softening modulus of surrounding rock. While consider- ing spatial effect when the shorter distance from excavation face to supporting face named value of x is,the bigger stress and displacement are and when value of x is greater than 10 m,the spatial effect is fail basically. Dilatancy coef- ficient h3 has a more important influence than h2 for surrounding displacement. Surrounding displacement of chamber under anchor bolt of different lengths can provide reference for the reserved rock deformation of supporting structure. The study in this paper can provide a theoretical basis for excavation-supporting of chamber.