Abstract: How to correctly evaluate the total porosity and fracture porosity of coal is very important to the exploration and development of coal bed methane (CBM). There is no effective method to evaluate the CBM according to the log data. In view of the methods of NMR experiment to obtain porosity cost much and make by spot measurement, so we propose the new method to effectively evaluate the fracture porosity of coal seam by electrical resistivity logging data and NMR experiments，in which the porosity from the resistivity is corrected by the NMR data , based on the pore structure and fracture porosity of coal seams from NMR experiments and applicability of Archie formula in the coal. The results showed that the T2 spectrum clearly showed two peaks, The left peak indicates adsorption pore, and the morphology change is small after centrifugation; the porosity calculated by Archie method largely reflects the fracture porosity of coal seam; The precision of coal fracture porosity corrected by NMR experiments is higher.