Abstract: Improving the resolution and increasing the detection range have been the key problems of electromagnetic wave CT detection in the working face. In this paper, the regularization inversion algorithm and emitting-receiving system of low frequency were adopted to realize the purpose of the fine electromagnetic wave detection with high resolution and large detection range. The detection results of engineering application and verification showed that improving the resolution by regularization inversion algorithm was feasible to detect the internal structure of the working face with the width over 250 m. The study can provide reliable data for the safe mining of the wide working face, so it has a promising application prospect.