<p>Rubella is a virus that can cause severe complications, such as congenital rubella syndrome, in pregnant women and newborns. Most clinical laboratories currently use qualitative methods to detect IgM antibodies; however, these have limitations in determining disease severity and progression. Thus, a quantitative IgM assay is required to enhance clinical diagnosis and treatment. Therefore, we employed the principle of the capture method for detecting rubella virus (RV) IgM. RV IgM was captured using anti-human IgM antibodies immobilized on magnetic beads, followed by adding Tm³⁺-labeled RV detection antigen, before performing inductively coupled plasma mass spectrometry (ICP-MS) analysis. The method demonstrated excellent linearity with a correlation coefficient (<i>R</i>²) of 0.9944 and a detection limit of 5 U/mL. Precision testing showed that the coefficients of variation (CV) for the low-concentration and high-concentration samples were 11.73% and 6.79%, respectively. Interference studies have shown that the bias from common interfering substances is less than 10%, and the method exhibits high specificity. The daily stability test results remained within 10%, while the recovery rate ranged from 95.25% to 102.43%. The reference interval for negative samples was less than 215.36 U/mL, and the kappa consistency test between our method and the electrochemiluminescence immunoassay method showed strong agreement, with a value of 0.86 (&gt;0.75). In conclusion, we have successfully established a quantitative antibody detection method based on ICP-MS and stable element labeling. The method met the Clinical and Laboratory Standards Institute standards, confirming its clinical applicability as a reliable tool for detecting RV IgM.</p>