Abstract: The construction of ultra-wide working face is helpful to promote the safe and efficient mining of coal resources. However, due to the limitation of roadway space and construction conditions, the detection depth of conventional mine geophysics is limited, and the geological information inside the ultra-wide working face and within a certain range of roof and floor cannot be accurately obtained. In order to improve the detection accuracy of the water rich area on the bottom plate of the ultrawide working face and provide a basis for the processing and interpretation of measured data, based on the summary and analysis of current mine geophysical detection technology, the three-dimensional(3D) DC resistivity method that can be applied to the detection of the ultrawide working face, combined with the occurrence characteristics of limestone water on the bottom plate of the working face 21106 in a coal mine in Yongcheng, Henan, was systematically studied using a combination of theoretical analysis, numerical simulation, and measured data to study the data characteristics and resolution ability of 3D observation and 2D observation modes. The research results show that: Compared with the traditional two-dimensional observation mode of the same side transmitter-receiver, the three-dimensional observation mode of the opposite side transmitter-receiver is more sensitive to the low resistance body on the floor of the mining face. The data obtained by the three-dimensional observation mode of the opposite side transmitter-receiver are calculated by the conventional apparent resistivity formula, the obtained apparent resistivity is sometimes opposite to the actual electrical property, so it is necessary to use the three-dimensional inversion method for data processing. Finally, the 3D model data observed during the 21106 work in a coal mine in Yongcheng, Henan Province was subjected to 3D inversion processing, and the reliability of the 3D inversion results was verified through underground drilling data. The research results provide a theoretical basis for the two-dimensional observation and three-dimensional observation data interpretation of the pole-pole device conditions.