Abstract: ObjectiveTo investigate the effect of Prunella vulgaris L.on the proliferation of different pathological types of thyroid cancer cells, and to screen the most sensitive thyroid cancer cell lines to Prunella vulgaris L.MethodsMTT colorimetrie assay was used to determine the effects of Prunella vulgaris L. at levels of 2.00, 5.00, 10.00, 20.00, 40.00, 80.00, 160.00, and 200.00 mg/mL for 24 h on proliferation of human normal thyroid follicular epithelial cells（HUM-CELL 0097), papillary thyroid cancer cell（K1）, and medullary thyroid cancer cell（TT）, 5.42, 10.84, 21.75, 43.44, 86.88, and 173.75 mg/mL for follicular thyroid carcinoma cells (FTC-133), and 1.56, 3.13, 6.25, 12.00, 25.00, 50.00, 100.00, and 200.00 mg/mL for thyroid squamous cell carcinoma cells (SW579), separately.ResultsThe half maximal inhibitory concentration (IC50)of Prunella vulgaris L. to HUM-CELL 0097, K1, TT, FTC-133，and SW579 for 24 h were 12.91,2.43,3.44, 6.95, and 31.15 mg/mL, respectively.The highest inhibitory concentrations were 20.00,80.00, 40.00, 86.88, and 100.00 mg/mL respectively.ConclusionPrunella vulgaris L. has different degrees of inhibiting proliferation to different pathological types of thyroid cancer cells. The papillary thyroid cancer cell K1 was the most sensitive to Prunella vulgaris L.among the five cell lines.