Taking the chamber group of the underground powerhouse of a proposed pumped storage power station as an example，considering the complex geological conditions including faults and veins，the three-dimensional numerical method is used to calculate the surrounding rock excavation process and the surrounding rock stress characteristics of the spray-anchor support process.Furthermore，the effect of the implementation of the spray anchor support was evaluated.The results show that after the excavation of the chamber，the intersection of the diverticulum and the fault and the interstitial layer of the vein， the deformation of the surrounding rock is abrupt， and the displacement is reduced after the support measures are completed.Significant stress concentration occurs at the local location of the fault and the vein interlayer and the abutment of the cavern，the intersection of the wall and the floor of the cavern.The support measures change the distribution of the stress field of the local surrounding rock，so that the local surrounding rock compressive stress increases，and the tensile stress is reduced.The distribution and location of the plastic zone of the surrounding rock of the cavern are basically the same.The distribution of the plastic zone of the surrounding rock of the cavern decreases with the increase of the support strength.The support measures effectively reduce the surrounding rock of the cavern plastic zone.Judging from the deformation of surrounding rock，characteristic stress and distribution of plastic zone，the effect of supporting the diverticulum of the underground powerhouse is obvious，which can improve the stability of surrounding rock.