In tunnel advanced exploration, the lateral focusing resistivity method has become a common method in logging. The authors carried out researches on the electrode assemblage of the three-dimensional tunnel DC focusing method. Based on the calculation and analysis of the current distribution regularity of two like point electric sources, this paper points out that, due to the mutual repellency of the current, the current density will produce the maximum value at a certain depth below the perpendicular bisector of the two point electric sources, and this depth is in direct proportion with the distance between the two point sources. On such a basis, the authors designed three kinds of electrode assemblages, i.e. four-point electric sources, five-point electric sources and nine-point electric sources. Then, the three-dimensional finite element digital simulation method was used to calculate the spatial potential distribution of these three electrode systems. The results show that the nine-point electric source type can yield fairly good current beam bunching effect and, moreover, the effect of the current seems to be the best when the current of the principal electrode is lower than the current of the shielded electrode.