Tianjin, as one of the pilot cities in urban geological survey, possesses specific geological conditions and deep overlying strata. During the urban three-dimensional geological structure survey, especially in the deep coverage areas, the method in which combined gravity-magnetic-electrical explanation and different inversions by mutual verification and combined explanation are adopted has proved to be very effective in detecting such phenomena as the depth, distribution and thickness of the main stratigraphic boundaries, the plane spread of the surface fractures and the deep-seated faults and the distribution of the concealed rock bodies. This paper deals with the application of combined gravity-magnetic-electrical explanation method exemplified by the cross section along Z14 line. This technique is of great reference value in the survey of three-dimensional geological structures in other cities.