With the development of information technology in geotechnical engineering, Underground Space and Engineering System (DUSES), a digital product was introduced. It is a managerial platform, which can provide information sharing and analysis for the construction, the management, the operation and the maintenance of the underground engineering. Its main functions include 3D modeling, visualization, data query, spatial analysis and so on. However, the supreme deficiency of DUSES lies in the fact that it cannot be introduced into numerical analysis to guide engineering practice. So it is necessary for the underground engineering, the resource sharing of the strata information and the numerical analysis to realize the integration of DUSES and numerical analysis. The paper describes an extension for DUSES that enables to perform finite element analysis by integration. Firstly, the integration mode of the system is researched and a combined type (embedded and loose coupling) is presented. That is to say, the numerical modeling is embedded into the function of DUSES and the modeling module is exploited; the calculation and the result feedback are performed with the loose data conversion module. Secondly, the contents of the integration are discussed in detail from the aspects of function, data and technique. The general framework of implementation is established. Finally, to illustrate the applicability of the proposed method, one example is provided. The results show that the integration of digitalization and numerical analysis can extend the professional analysis functions of DUSES. By employing the integration technique, mechanical analysis in partial region can be optionally implemented and the project design can be optimized. For the numerical analysis system, the automatic modeling can be realized by extracting the data from database. The efficiency of preprocessor and the accuracy of the calculation results can also be largely improved. The proposed technique will give some useful references for the continuous research on this subject.