Abstract: At present, TBM (Tunnel Boring Machine) has been widely adopted in major national tunneling projects such as highways, railways and water conservancy, and it has been gradually used in coal mine roadway excavation. During shield tunneling operations, the deployment of geophysical advanced detection techniques is imperative to mitigate water inrush hazards associated with concealed water-bearing structures. However, when TBM completely occupies the tunnel space, there is no construction space for conventional transient electromagnetic advanced detection. To address this technical challenge, this study proposes a surface-tunnel transient electromagnetic-while-tunneling advanced detection method in TBM tunnels, in which one fixed electrical source is laid on the surface, and eight electrodes are mounted on the shell of TBM to form a multi-component observation array for coordinated observing the transient electric field in the surrounding rock. Geophysical models for surface-tunnel transient electromagnetic-while-tunneling advanced detection of electrical source are established. Numerical simulations of the spatiotemporal distribution of subsurface transient electric fields of electrical source are performed using the finite-element method with unstructured tetrahedral meshes. The results of the study show that: When the electrical source is perpendicular to the excavation direction and its midpoint deviates a certain distance from the tunnel axis, three-component transient electric fields are successfully acquired, and anomalous responses induced by low-resistivity anomalous body can be observed around the tunnel. The x-direction electric field is more sensitive to the spatial position change of the low-resistance anomalous body, and the position is qualitatively interpreted through the combination of anomalous responses characteristics of six electric field components. The y-direction and z-direction electric fields are more sensitive to the distance change between the low-resistance anomalous body and the excavation face, and analyzing amplitude changes of these electric fields enables detection of distant low-resistivity anomalous body. With a 5% amplitude difference as the detection threshold, a detection range of 60 m is achievable for a low-resistance anomalous body measuring 50 m×50 m×10 m with a resistivity ratio of 1:100 to the surrounding rock. This research provides a new approach for the realization of tunneling-exploration integration in TBM tunnels, and offers a theoretical basis for the surface-tunnel transient electromagnetic-while-tunneling advanced detection. However, a systematic processing-interpretation methodology has not been established. Future work will focus on correcting strong electromagnetic interference from TBM and deriving the formula of subsurface whole space apparent resistivity.