Due to the limit of Surpac software, the method for 3D numerical grid generation based on the Surpac software generally suffers for some deficiencies such as time-consuming and cumbersome. By adopting the basic idea of octree subdivision, the batch and automatic meshing technology of multiple geological body is investigated. To resolve the confliction issue arising when both the precision and the model scale need to be considered in computation, the grid local encryption and multi-scale partitioning methods are introduced and discussed based on the concept of multiple grid method. An automation software platform is developed for 3D numerical grid generation by using VC++. The platform can be conveniently and effectively used to generate the numerical grids for the mining fields with complex geomorphology, providing a strong support for the automation of excavation numerical analysis. The new platform has been used in the in-situ stress inversion analysis of Linglong gold mine, showing its applicability and capability.