Abstract: In order to realize the effective detection of electric field focusing depth and deflection angle scanning of focusing multipoint current sources in coal mine roadway, and accurately grasp its variation, according to the advanced scanning detection mechanism, Gauss theorem and two different methods were used to solve the integration process and derive the electric field line equation of a uniformly charged linear electrode with finite length. The electric field line equation of coplanar multi-electrode layout is induced and deduced through using its spatial distribution symmetry. By changing focusing shielding current ratio coefficient, this paper calculates the boundary line equation of effective detection electric field lines and analyzed the variation of average current density and spatial angle. The lower boundary angle and the deflection angle variations of the electric field boundary line were analyzed through changing simultaneously focusing and deflection shielding current ratio coefficients. The range of emission current intensity of the main electrode and the constrained electrode for advanced scanning detection was determined. This research will provide a technical guidance for the electric survey of focusing multipoint current sources in the field, and is of great significance for improving the exploration mechanism of focusing electric method and promoting the development of geophysical theory.