Abstract: A conceptual framework of mine complex fields is proposed from the perspective of numerical modeling and visual simulation for geological and mining engineering systems. In view of the current trends towards the advancement of so-called digital mines using computation, information and communication technologies, the significance of developing the unified numerical modeling and integrated 3D visualization systems for mine complex fields composed of geological and mining objects and their attributes is emphasized. Oriented to the needs for developing the techniques and systems of digital mines, key issues in and major methods for numerical modeling and 3D visual simulation of mine complex fields are presented. Fitting into the framework and using the proposed methods, a prototype system with a Web-based approach for the numerical modeling and 3D visualization of geological drill holes, ore bodies and underground excavations is built to show the methodologies used in constructing the prototype and the usefulness of a unified numerical modeling and 3D visual simulation approach in addressing the problem of complex fields in underground mines.