Co-delivery of antitumor agents has a potential to efficaciously treat human diseases via their synergetic effects.In this report, we prepared nanoparticles(NPs) for co-delivery of cisplatin (CDDP), a widely used chemotherapeutics and tetrandrine (Tet), an alkaloid isolated from the Chinese herb using PEG-PCL/PCL copolymer hybrid.By w/o/w double emulsion method, CDDP and Tet were incorporated into the NPs with the loading content of 3.32% and 7.45% respectively.In vitro studies showed that drugs loaded in NPs enter LoVo cells by cellular uptake of NPs.On three different cancer cell lines, CDDP and Tet showed a synergistic antitumor effect after incorporated into NPs while antagonistic effect was detected when they used as free drugs.Intracellular concentration studies revealed that the intracellular concentrations of CDDP and Tet were significantly increased when they were delivery by NPs.