Objective To investigate the expression of ten-eleven translocation 1 (TET1) of different types of endometrial lesions and the effects of intervening the expression of TET1 on biological behaviors of endometrial cancer cell line Hec-1a and Ishikawa cells. Methods The expression of TET1 was detected by the immunohistochemistry. TET1-siRNA was designed, synthesized, and transfected to Hec-1a and Ishikawa cells. Cells with transfection reagent served as negative controls. The efficiency of transfection was detected by the Western blotting. Variations of proliferation, invasion, migration, and cycle of cells were detected by the SRB, Transwell assay, wound scratch assay, and flow cytometry, respectively. Results The expression of TET1 in endometrial tissues increased with the development of pathologic types. The expression of TET1 of the intervention group was significantly lower than that of the control group. The proliferation, invasion, and migration of endometrial cancer cells were more or less inhibited and cell cycle was arrested at G1/S phase after the expression of TET1 was intervened. Conclusion The expression of TET1 in tissue of endometrial hyperplasia and endometrial cancer is significantly higher than that in normal tissue. The proliferation, invasion, and migration of endometrial cancer cells are inhibited and cell cycle is arrested at G1/S phase after the expression of TET1 was intervened, which suggest that TET1 plays an important role in the proliferation and migration of endometrial cancer cells.