Abstract: Referring to the hemodialyzer instructions and GB/T 14232.1—2020, water and ethanol-water mixed solution were used to extract leachable substances from the hemodialyzer. The chromatography and mass spectrometry information of unknown leachable substances in the extract was collected by liquid chromatography-high resolution mass spectrometry. The qualitative process was introduced using dimethylacetamide as an example, and the content of leachable substances was determined by external standard method. It was shown that 3 leachable substances were found around 1.7, 2.1, 2.5 min, which were determined to be 2-pyrrolidone, dimethylacetamide, and N-methylpyrrolidone after mass spectrometry analysis and comparison with reference substances. Linear relationships between values of the mass concentration of 3 leachable substances and the corresponding peak area of quantitative ions were kept in the ranges of 0.089 6−4.48 mg·L⁻¹, 0.469 5−18.78 mg·L⁻¹, and 0.102 6−5.130 mg·L⁻¹, with detection limits (3S/N) of 0.005 1, 0.009 9, 0.010 5 μg·g⁻¹. The method was used for the analysis of 28 hemodialyzers, and the leaching amounts of 3 leachable substances in ethanol-water extract were higher than those in water extract, with the maximum leaching amounts of 376.7, 2 668.4, 517.8 μg, respectively.