Objective In many types of epithelial tumors, downregulation or mutation of the epithelial celladherent molecule E-cadherin is associated with an increased invasiveness that can be prevented by the forced expression of the celladherent molecule. This suggests that E-cadherin is a latestage tumor suppressor that prevents invasion and metastasis. This study was to investigate cell invasion and migration status of human ovary serous cystadeno carcinoma HO-8910 cell line when the E-cadherin expression was downregulated with RNA interference (RNAi) technology. Methods E-cadherin siRNA was transfected into HO-8910 cells to inhibit the expression of E-cadherin. The effect of RNAi was detected by immunofluoresence assay and Western blotting. The invasive ability of the cancer cells was determined by Transwell assay. Results After RNAi, the expressions of E-cadherin were significantly decreased from 63.7% to 11.9% (P<0.01 ), which indicated that RNAi was effective. The cells invasion abilitiy and migration abilitiy were significantly increased. The cells that invaded through the basement membrane filter were increased from 13.4±3.93 to 42.04±4.15 (P<0.01) while the cells that migrated through the basement membrane filter were increased from 23.24±3.71 to 82.0±5.51 (P<0.01).Conclu