Abstract: A method for the determination of platinum in geological samples by spectrophotometry with sulfhydryl fiber preconcentration was developed. After sample digestion, platinum in the sample solution was adsorbed with sulfhydryl fiber in the presence of stannous chloride （reductant） and hydrazine hydrate (assistant adsorbent). The adsorbent was then ashed and digested with aquae regia. Platinum in the sample solution was determined by spectrophotometry in didodecyldithiooxamide （DDO） system. Detection limit of the method for Pt is 0.2 μg/g with liner range of 0～20 μg/g. The method has been applied to the determination of Pt in National Standard Reference Materials and the results are in agreement with certified values with precision of less than 10%RSD (n=12).