Abstract: Initial stress field is the foundation for the computation and the analysis of engineering stability.More stability simulation of rock underground engineering proved that the widely used methods (i.e.，velocity boundary method and rapid stress boundary method) can generate the initial stress field moderately agreed with the practice in FLAC3D program；However，for deep engineering，the ground stress generated by the velocity boundary method is not consistent with the actual，and when using the rapid stress method，the boundary condition may be applied difficultly and the generated ground stress at the shallow level disagrees with the actual.Thus，by combining the advantages of the above two methods，the velocity-stress boundary method to generate the initial stress field of deep engineering is proposed in FLAC3D.Then，the loading range of the velocity boundary condition and the stress boundary condition of the model is discussed to determine.Finally，the reasonableness of the velocity-stress boundary method is proven by the analysis of an example.The results show that：the numerical model for deep engineering can be built by the velocity-stress boundary method and its loading range of velocity boundary and stress boundary condition may be determined through computing many times；the initial stress field generated by the velocity-stress boundary method consist with the measured data；The problems existing in the above two methods are solved.The results can serve as reference and guidance for the numerical simulation and analysis of deep mine engineering.

Key words: Deep engineering in mine, Initial stress field, Velocity-stress boundary method, FLAC3D