Abstract: As an ultra-trace heavy nuclides, Pu have important applications in fields such as nuclear environmental protection, nuclear astrophysics, and geological research. Accelerator mass spectrometry (AMS), with its low detection limits, high measurement sensitivity, and effective capability to overcome interferences from isobars and molecular ions, is the most suitable method for measuring Pu isotopes such as ²³⁹Pu and ²⁴²Pu. This work, based on the 300 kV AMS system at the China Institute of Atomic Energy (CIAE), conducted research on Pu measurement methods. The study primarily included investigations into negative ion extraction from the ion source, high-efficiency system transmission, background exclusion, and particle identification techniques. Ultimately, a high-efficiency transmission and high-sensitivity measurement method for Pu was established. Measurement results of standard samples were consistent with their nominal values and demonstrated excellent stability, with a detection limit of 2×10⁶ atoms (0.8 fg) for ²³⁹Pu.