The tunnel DC resistivity advanced detection method is a method based on the theory of equipotential spherical surface that is excited by point source in full space. Due to the existence of a considerable impact from tunnel and detection environment when the measurement is performed at the rear of the heading face, difficulty in data interpretation is largely increased. On the basis of vertical ground resistivity sounding and side DC logging technology, the authors proposed a vertical focused advanced detection project which is suitable for tunnel space. The finite element numerical simulation method (FEM) was used to simulate the effect of focused advanced detection method in three-dimensional tunnel space. Compressed storage technology and preconditioned iterative algorithm could greatly improve the efficiency of forward modeling as well. A comparison between the FEM modeling results and the physical simulation results in a soil bin shows that the accuracy of forward simulation can meet the requirement, and the vertical focused device can attain the purpose of focused advanced detection. The results of simulated complex models under the condition of vertical focused observation show that the scheme can effectively detect ill geological bodies in front and side tunnels.