Abstract: There are big differences among igneous reservoirs with similar physical and fluid properties, but the reason for the differences is not clear. Taking the Carboniferous igneous rocks in District Dixi of Junggar basin as an example, the paper analyzes the application effect of NMR data from 3 wells and discusses the differences of the NMR data application effect from 3 aspects such as ferromagnetic mineral content, quartz content and shale content. The result shows that the application effect of NMR data in acidic igneous rock study is better than that in intermediate-basic igneous rock study. The calculated porosity obtained from NMR logging decreases with the increase of ferromagnetic mineral content, which is closer to the actual formation porosity with the increase of quartz content and becomes larger with the increase of shale content. The variation of the porosity is less than 10%