Abstract: Objective To explore the relationship between the expression of Cyr61 and the chemosensitivity, apoptosis of human glioma U251 cells by decreasing Cyr61 gene expression by RNA interference. Methods One pair of DNA template coding siRNA was synthesized against U251 to reconstruct pRNA-Cyr61, which was transfected into U251 cells. The Cyr61 expression in U251 cells was transfected with pRNAT-Cyr61, and it was detected by RT-PCR and Western blot. MTT and flow cytometry (FCM) were used to observe the growth inhibiting ratio and apoptosis rate induced by cisplatin or temozolomide in U251 cells. Results RT-PCR and Western blot analyses demonstrated that pRNAT-Cyr61 could significantly inhibit the expression of Cyr61 in U251 cells (P<0.01); MTT and FCM showed that when U251 cells were exposed to cisplatin or temozolomide, the growth inhibiting ratio and apoptosis rate of pRNAT-Cyr61 transfected cells were significantly increased compared with those of control group and negative group (P<0.01). Conclusions pRNAT-Cyr61 can significantly inhibit the expression of Cyr61, increase chemosensitivity and apoptosis rate of U251 cells in vitro.