Abstract: In order to investigate the influence of original rock stress on the stress of plastic zone, SMP(Spatially Mobilized Plane) criterion is used as elasto-plastic analytical method of circular chamber. Under the conditions that the stress is continuous at the elastic-plastic interface and periphery of chamber, the computational formulae of chamber surrounding rock stress and the supporting force are obtained. The studies show that the plastic stress and support pressure are not only related to the mechanical properties of itself but also in-situ stress. And through numerical examples, we analyzed the influence of original rock stress on the plastic zone stress and the supporting force. It is well worth notice that the stress of the plastic zone increases with the increase of the original rock stress, and increases gradually along the depth of the surrounding rock. Similarly, the results obtained the stress of plastic zone and the support pressure has significant linear relationship with the in-situ stress.