Abstract: The results of 3D electrical resistivity detection are non-unique, and could easily lead to errors in geological interruption and even misjudgment. A solution is proposed to solve this problem, in which the reference model constraints constructed by the known information from other geological methods are applied to the inversion equation. The electrical resistivity information is gained by the geological drilling, and the boundary information of anomalous bodies is obtained from ground penetrating radar (GPR). All the known information is mapped into the 3D inversion and then the reference model is obtained, which is introduced to the electrical inversion. Then the 3D constrained electrical resistivity inversion method based on the reference model is got. In this method, the reference model constraints containing the prior information can guide the direction of the inverse progress and make the inversion avoid falling into local optimization. This method can reduce the multiplicity of the inverse solutions in theory. The numerical tests and engineering applications are implemented. The results show that the proposed inversion method can map the shape, size, resistivity of the abnormal body well, and is a practical way to integrate information from multiple geophysical explorations and to suppress the multiplicity.