Abstract: Objective: To explore the feasibility of using vector-based small Interfering RNA (siRNA) to reverse the multidrug resistance in drug-resistant ovarian cancer cell line. Methods: An adriamycin-resistant human ovarian cancer cell subline (OVCAR/AR) was established by stepwise inducement. Transfection of MDR1 mRNA specific siRNA expressing plasmids (pSN/mdr1a and pSN/mdr1b) into OVCAR/AR cells was performed using liposome transfection reagents. MDR1 mRNA expression level was quantified using real-time reverse transcription polymerase chain reaction (real time RT-PCR). Flow cytometry (FCM) was performed to assess the expression of p-glycoprotein (P-gp). The transporting function of P-gp was determined by Rhodamine assay. Multidrug resistant to anticancer agents was evaluated by MTT assay. Results: Basal MDR1 mRNA and P-gp expression level in drug-resistant cell line OVCAR/AR was higher than that in its parent cell line OVCAR-3. After transfection with pSN/mdr1a and pSN/mdr1b, the expression level of MDR1 mRNA and P-gp protein was reduced. The transporting function of P-gp to drugs was reduced simultaneously. Treatment of OVCAR/AR cells with pSN/mdr1a and pSN/mdr1b resulted in a different level of reversal of drug-resistantance to P-gp mediated drugs Adriamycin and Paclitaxel. Conclusion: Vector-based MDR1 specific siRNA can inhibit the expression levels of both MDR1 mRNA and P-gp continuously and effectively, thereby to sensitize their Adriamycin-resistant ovarian cancer cells.