This research aims to establish a three-dimensional model of the underground environment through a patented fully integrated visual navigation/inertial navigation method and a three-dimensional model reconstruction technology in close-range photogrammetry technology, and restore scene information to survey urban underground infrastructure. The main research content includes the application of a patent-based fully combined visual navigation/inertial navigation method in underground environments. Research on three-dimensional reconstruction technology in complex underground environments with low light and weak texture includes real-time modeling research and three-dimensional modeling technology research for dense point clouds.