Abstract: Objective To establish a triple negative breast cancer cell line MDA-MB-231 with the characterization of cisplatin (DDP) resistance, and investigate its biological mechanism of drug resistance. Methods A DDP-resistant human triple negative breast cancer cell line MDA-MB-231/DDP was obtained discontinuously by gradually increasing doses of DDP. The drug resistance of MDA-MB-231/DDP cells was evaluated by MTT assay. The variation of intracellular concentration of DDP in MDA-MB-231/DDP cells was evaluated by HPLC. The expression of MDR1, BCRP, MMP7 and GST-π were detected by Real-time PCR. Results The cisplatin, 5-Fu and CTX were acting on MDA-MB-231/DDP and the resistance fold (RF) were 9.80, 4.43 and 2.21. After treated with 6μg/ml DDP for 24h, the concentration of DDP in MDA-MB-231 and MDA-MB-231/DDP cells were (47.10±2.37)ng/(5×10⁴) cells and (6.30±1.64) ng/(5×10⁴) cells (P<0.01). The expression of MDR1, BCRP, MMP7 and GST-π mRNA in MDA-MB-231/DDP cells were 15.39, 13.73, 22.52 and 44.90 times the expression of those in the parent cells. Conclusion A drug-resistant cell line MDAMB-231/DDP with high resistance fold is established by discontinuous induction and gradually increasing doses of DDP. The resistance mechanism may be associated with the increased expression of ABC transporter