Abstract: The YAP∶Ce scintillator was selected as a core component for the instrument, and a contact-type measurement of micro and trace plutonium α activity in solution was established. The results show that under the aqueous phase plutonium solution concentration from 5.20×10^-5 g/L to 1.30×10^-3 g/L, the concentration of plutonium and net count rate have fine linearity (R²=0.987 7), and the quantitative detection limit is 5.20×10^-5 g/L. Under the organic phase plutonium solution concentration from 2.27×10^-5 g/L to 1.13×10^-3 g/L, the net count rate and the concentration of plutonium have fine linearity (R²=0.992 3), and the quantitative detection limit is 2.27×10^-5 g/L. The method is different from the traditional α-counting method, and has the advantages of simple and convenient operation and without complicated sample preparation process. It is expected to provide a new way for micro and trace plutonium determination online or in laboratory in spent fuel reprocessing.