Techniques for high_precision measurements of Fe isotope ratios using MC-ICP-MS at both low-and high_resolution modes have been reported in detail, which includes assessments of isobaric inferences, matrix effects, concentration effects and long_term repeatability. The external precision for the methods established at both low-and high-resolution modes are better than 0.5 ε/amu, and the results obtained under the two modes are consistent with each other. Using the techniques developed, the Fe isotope compositions of national geological reference materials GBW 07105 (basalt powder) and GBW 07111 (grano-diorite powder) have been measured. Relative to IRMM-14, the Fe composition for GBW 07105 is: ε57Fe＝1.9±0.3(2σ)，ε56Fe＝1.3±0.2(2σ)，ε57/56Fe＝0.6±0.1(2σ)； and ε57Fe＝1.8±0.4(2σ)，ε56Fe＝1. 2±02(2σ)，ε57/56Fe＝0.6±0.1(2σ) for GBW 07111.