Abstract: Objective:To construct an endoglin siRNA expression vector and observe it's silencing and anti-angiogene -sis effects on endothelial cells of ovarian carcinoma. Methods:According to the endoglin cDNA sequence in GenBank, two target sequences were designed and synthesized. After annealing, oligonucleotides were inserted into pGenesil- 1 vector. The recombinant plasmid was identified by DNA sequencing. pGenesil-ENG 1 and pGenesil-ENG2 were transfected into ovarian carcinoma-derived microvascular endothelial cells (ODMECs) with Lipofectin. After 48hours, expression levels of endoglin mRNA was assayed by RT-PCR. MTT assay was used to observe the proliferation of transfected and untransfect-ed control ODMECs. The formation of two dimensional tubular structures of ODMECs was observed in vitro by light micros-copy after transfection of pGenesil-ENG1. Results: Sequence analysis of the inserted fragment validated the successful construction of the eukaryotic expression plasmid of endoglin. After 48h, ODMECs transfected with the recombinant plas -mid showed decreased expression of the endoglin mRNA and significant suppression of cell growth (P<0.01). Transfected ODMECs also showed significant reduction in the invitro two-dimensional formation of vessel-like structures (P<0.01). Conclusions: The endoglin siRNA expression vector has been successfully constructed. It effectively downregulated the expres-sion of endoglin in ODMECs, thereby inhibiting proliferation and two-dimensional lumen-like structure formation.