Exact-matching double isotope dilution inductively coupled plasma mass spectrometry (ID-ICP-MS) is most reliable measurement method. Thus, it is frequently used for the characterization of reference materials for elemental analysis. In this method, the same amount of isotopically enriched material of the target element is spiked to both the sample and a calibration standard solution to closely match the isotope amount ratios of the respective mixtures. Under this experimental condition, many components of measurement uncertainties are cancels out. However, achieving exact matching condition needs a number iterative experimental process. In this study, possibilities to minimize the attempts needed to achieve this condition were investigated by evaluating the influence of in-exactly matching in double IDMS on the final mass fraction results. The mass fractions of Ca, Cd, Cu, Fe, Hg, Mg, Ni, Pb and Zn was measued in a samples of wheat flour certified reference material (KRISS-108-01-006), deliberately prepared to have in-exactly matched isotope ratios. All the results obtained were in good agreement with the values in the certificate. This implies, in-exact matching in blends isotope ratio over the studied range do not alter the accuracy of IDMS results. Slight errors; however, are observed in Ni and Zn results and further investigation is ongoing.