Abstract: In this study, high-performance liquid chromatography coupled with tantrum mass spectrometry (HPLC-MS/MS) technology was employed to determine milrinone nitrogen oxides in milrinone. An ACCHROM XCharge-C₁₈ column (100 mm × 2.1 mm, 5 μm) was used with a mobile phase consisting of A phase (methanol) and B phase (5 mmol/L NH₄FA, pH3 adjusted by formic acid). Agilent 6410B triple quadrupole mass spectrometer was used for HPLC-MS/MS analysis. Detection was performed using positive electrospray ionization (ESI⁺) in multiple reaction monitoring (MRM) mode to analyze the limit of milrinone nitrogen oxides in milrinone, and the quantitative transition for the ion pair was from m/z 228.01 to m/z 181.90. Experimental results showed that the method exhibited good specificity, and that neither blank solvent nor blank samples interfered with the determination of milrinone nitrogen oxides of milrinone. The method demonstrated high sensitivity, with a limit of quantitation (LOQ) of 0.0076 μg/mL and a limit of detection (LOD) of 0.0038 μg/mL. The linear range spanned from 20% to 200% of the LOQ concentration, and a good linear relationship between concentration and peak area was observed within this range. Additionally, the recovery rates were consistently within the range of 80% to 120%, and the RSD for repeatability tests was 12.0%. These results indicated that the precision and accuracy of this method meet the required standards. In summary, the method developed in this study can effectively and accurately determine the content of milrinone nitrogen oxides in milrinone.