Discussion and evaluation of traceability and uncertainty are introduced to determine results of copper-nickel-sulfide Re-Os reference material which was prepared under the technique guideline for national first grade standard material. The contents of Re-Os and the isotope ratio of 187Os/188Os can be traced to benchmark materials and IUPAC, respectively. The uncertainty of the data was calculated by using the authoritative ISOPLOT program for data processing. The total uncertainty was combined with homogeneity and stability of the reference material, the uncertainties of contents and compositions for spike solutions, weighting error and other factors.