Abstract： Objective： To observe the effect of ursolic acid on the expressions of estrogen receptors ERα and ERβ，and to study the mechanism of ursolic acid in inhibiting proliferation，migration and invasion of thyroid cancer BCPAP cells. Methods：The protein expressions of ERα and ERβ in human normal thyroid cells (Nthy-ori3-1 cells) and thyroid cancer BCPAP cells were detected by Western blot. The effect of ursolic acid on the proliferation of thyroid cancer BCPAP cells was detected by CCK-8 assay. The effect of ursolic acid on the migration and invasion of thyroid cancer BCPAP cells was detected by cell scratch assay and Transwell assay. The effect of ursolic acid on the expressions of estrogen receptor ERα and ERβ in thyroid cancer BCPAP cells was detected by Western blot. Results： Compared with BCPAP cells， the expression level of ERα was lower in Nthy-ori3-1 cells (P＜0.05)， and the expression level of ERβ was relatively high (P＜0.05). Ursolic acid at different concentrations (4， 8， 16， 32， 64 μmol/L) inhibited the proliferation of BCPAP cells in a time- and concentration-dependent manner (P＜0.05). The migration of BCPAP cells in the B4 group (4 μmol/L) and the B8 group (8 μmol/L) was lower than that in the B0 group (0 μmol/L) at the same time point (P＜0.05). Compared with the B0 group， the number of invasive BCPAP cells in the B4 and B8 groups was significantly decreased (P＜0.05). After 24 hours of treatment with ursolic acid，the expression level of ERα in the B4 and B8 groups was lower than that in the B0 group (P＜0.05)， and the expression level of ERβ was higher than that in the B0 group (P＜0.05). Conclusion： Ursolic acid may reduce the proliferation， migration and invasion of thyroid cancer BCPAP cells through estrogen receptors ERα and ERβ.