Salviae miltiorrhizae radix et rhizoma is a traditional herbal medicine with anti‐cancer activities. In this work, a trace peak enrichment approach combined with a cell proliferation assay was applied for screening cancer cell proliferation inhibitors from the extract of S. miltiorrhiza. A set of 123 peak fractions were prepared, and by comprehensive screening, 21 tanshinones were screened out as cancer cell proliferation inhibitors and their structures were tentatively identified by liquid chromatography coupled with quadrupole time‐of‐flight tandem mass spectrometry analysis. The inhibitory activities of nine available screened tanshinones were validated, with their IC50 values ranging from 0.63 to 28.40 μM, indicating their activities strongly inhibit the proliferation of cancer cells. This study presents tanshinones that are potential cancer cell proliferation inhibitors and may explain the anti‐cancer activity of S. miltiorrhiza.