Abstract: Aprocedure was established for the determination of Mo and Fe in Mo-Fe-Scluster compounds by atomic absorption spectrophotometry with graphite furnace atomizer. It has significant advantages over the traditional technigues for the analysis of samples containing less than 1% Mo or Fe or of very small samples.The sensitivities are 10 ppb for Fe and 5 ppb for Mo. There is no interfere between different elements and the pretreatment of sample is simple.The recoveries of both Mo and Fe are 100±5% and the precisions (as variance coefficients) Fe<4% and Mo<2% in the concentration range of 0.1-1.0 ppm Fe or Mo.