结合瀑布沟水电站厂房区地应力实测资料，考虑地形地势建立大范围的整体模型，采用遗传算法和有限单元法对其初始应力场进行一次反演。在此基础上，考虑主要断层等细部构造，建立地下厂房洞室群小范围精细子模型，采用位移边界条件，对子模型进行二次有限元计算，得到该区域更为准确的初始地应力场。分析结果表明：一次反演简单，主要考虑地形地势的影响，消除边界应力分布的影响，可反映大范围初始地应力的分布规律；考虑主要地质构造的二次计算，可以得到细部构造处的初始地应力，反映局部地应力的分布规律，并且改善了一次反演的误差范围。二者联合应用能高效获取更为准确的初始地应力场，为工程设计与施工奠定了良好基础。

A large-scale monolithic model is established considering mainly the topographical influence nearby the project, and with stress measured data in Pubugou Hydropower Project. So the initial geostress field is back analyzed firstly by genetic algorithm and finite element method. On the basis of considering influences of some main geological structures, the refined sub-model used in the stability analysis of the caverns is accomplished, and the more precise initial geostress field of the sub-model is obtained by the second finite element analysis iteratively using displacement boundary conditions. The results show that: the first inversion is simple, with considering mainly the topographical influence and eliminating the stress distribution of the borders, its results reflect the distribution law of the large-scale initial geostress; by the second calculation considering some main geological structures, the initial geostress of the detailed structure can be obtained, and the error range is reduced bythe second calculation. The more accurate initial geostress field can be obtained efficiently by this approach as a foundation for the engineering design and construction.