Abstract: An inductively coupled plasma-mass spectrometric (ICP-MS) method for determination of trace ruthenium and osmium in geochemical samples with distillation separation was established. The elimination of the interferences on ICP-MS measurements were studied through the experiments. Samples were decomposed with Na₂O₂ fusion method and the melts were dissolved with acid solution. KMnO₄+K₂S₂O₄+NaCl were added to the sample solution as an oxidant and 20 mL 5% hydrazine hydrate was selected as an absorbent. Trace ruthenium and osmium in the sample solution were separated by distillation from matrix and determined by ICP-MS. Distillation conditions, such as temperature, time, oxidant and absorbent were tested and optimized. The detection limits of the method were 0.020 ng/g for Ru and 0.015 ng/g for Os. Recoveries of the method were 94.0%~102.7% for Ru and 96.0%~102.4% for Os with precision of 4.72%~9.58%RSD(n=12) for both elements. The reliability of the method has been tested by determination of trace Ru and Os in National Standard Reference materials and the results are in agreement with the certified values.