Under the conditions of according with strain nonlinear softening constitutive model of having inflexion point after peak stress of practical rock and considering rock deformation influence due to intermediate principal stress ，stress distribution laws of surrounding rock plastic zone of circular cavern under the condition of uniform pressure，the mechanism of load bearing and acting relation between surrounding rock and support are studied. Some important conceptions of working status of practical cavern surrounding rock are obtained；such superior certain limit sup{pos} of self-support geo-stress and inferior certain limit inf{pa} of supportless cavern surrounding rock. The expressions of sup{pos}

inf{pa} and the relation formula between sup{pos}and geo-stress ，between inf{pa}and geo-stress p0 are given. The research results of plastic zone stress，plastic zone radius，surrounding rock pressure，and surrounding rock displacement are more nearly actual correspondence values of cavern surrounding rock with Fenner solution based on ideal elastoplastic materials.