〔Abstract〕 Objective To investigate the expression of microRNA-34 a(miR-34 a) and silent information regulator 1(SIRT1) in the placentas of patients with pre-eclampsia and the effect of miR-34 a on the expression of SIRT1 as well as the proliferation and apoptosis in HTR-8/SVeno cells. Methods Placental tissues were collected from patients with pre-eclampsia(n=30) and normal pregnant women(n=30). MiR-34 a mimic, miR-34 a inhibitor and SIRT1 siRNA were transfected into HTR-8/SVeno cells. The expressions of miR-34 a and SIRT1 were measured by qRT-PCR and Western blot. Cell proliferation was determined by MTS assay. Apotosis was detected by flow cytometry. Results The relative expression of miR-34 a was significantly elevated and SIRT1 significantly reduced in the preeclamptic placentas. Transfection with miR-34 a mimic in HTR-8/SVeno cells decreased the expression of SIRT1 mRNA and protein. Meanwhile, the rate of proliferation significantly decreased, whereas the rate of apoptosis significantly increased. However, transfection with miR-34 a inhibitor showed the opposite results. Moreover, knockdown of SIRT1 significantly inhibited the rate of proliferation and increased the rate of apoptosis of HTR-8/SVeno cells. Conclusion MiR-34 a may participate in the development of PE by inhibiting the expression of SIRT1 and the proliferation of trophoblasts and inducing the apoptosis of trophoblasts.