Abstract: The optimum chromogenic conditions of the colored system that is ternary coordination compound Sc(Ⅲ)-CPA-pc-Ⅰ^- and its main characters were studied systemati-cally. The influence of some foreign ions on this colored system was measured. Beer's law is obeyed over a range of 0~7.5 μg Sc/25ml. The relative molar absorpbility is 1.4×10⁵ 1·mol^-1·cm^-1. The system was used to determine the trace amount of scan-dium in a synthetic sample and in Pan Zhihua magnetite, the results were satisfied.