A CSAMT detection test was carried out for a coal mine with V8 multi-functional electrical instrument. Due to the serious electromagnetic interference within the area, the Cagniard apparent resistivity was low in quality. In order to improve the quality and utilization rate of data, authors attempted to process the CSAMT data collected by V8 with the wide field electromagnetic method, which used single-component method and ratio method (Electric field divided by magnetic field) to calculate apparent resistivity. The results showed that there was some deviation between the single-component wide field apparent resistivity and the actual terrestrial electricity because the emission current was not measured during the construction of V8. The wide field apparent resistivity of ratio method was agree with the Cagniard apparent resistivity in the high frequencies but significantly better in the low frequencies, and consistent with the actual terrestrial electricity. In addition, the inversion results of the ratio method wide field apparent resistivity accurately reflected the interface between the coal measure strata and the Ordovician limestone. The geological interpretation corresponded well with the drilling results, which verified the feasibility and effectiveness of wide field electromagnetic method in CSAMT data processing for coal mines.The research results also provide references for CSAMT data processing of other mineral resources.