Due to the polymer, octylamine-graft-poly (aspartic) (PASP-g-C₈), which acted as acidic triggered molecules, liposomes anchored with PASP-g-C₈ (OPLPs) could be safe and efficient pH sensitive drug carriers and target tumor cells. In the present study cytarabine (CYT) was chosen as the model drug and the in vitro biological stability and cytotoxicity of OPLPs were further investigated. Transmission electron microscopy (TEM) images indicated that the OPLPs remained active in both normal (pH 7.4 solution) and tumor tissues (pH 5.0 solution). The particle size was maintained at about 350 nm. In addition, the results of atomic force microscopy (AFM) revealed that OPLPs could obviously promote the dent in HepG2 cell membrane and enhance its roughness, while they had a lower effect on vero cells. Flow cytometry (FCM) results showed that cell apoptosis of HepG2 cells induced by OPLPs after 48 hours reached 42.9%, one and a half times more than that induced by conventional liposomes (LPs(+)). Meanwhile, when vero cells were exposed to OPLPs after 24 hours, the cell apoptosis was 29.6%, less than half of that of LPs(+). The results illustrate that OPLPs not only possess good biological stability, but also have stronger cytotoxicity towards tumor cells as well as lower effect on normal cells. Based on these findings, the OPLPs may be a promising candidate in nanotechnology-based drug delivery.