Differential scanning calorimetry (DSC), Fourier transform infrared (FTIR) spectroscopy and quantum calculation based on molecular modeling were applied to investigate the interaction between pirarubicin (THP), an anthracycline antibiotic frequently used in chemotherapy, and zwitterionic distearoylphosphatidylcholine (DSPC) or anionic distearoylphosphatidylglycerol (DSPG). DSC and FTIR studies suggested that DSPG bilayers were less perturbed by THP than those of DSPC, and this might be due to the strong interactions between NH(3)(+) of THP and the phosphate (PO(2)(-)) group in the polar head of DSPG, which limit the further access of THP into its bilayers. Quantum calculation results based on molecular modeling could further confirm the DSC and FTIR conclusions. Meanwhile, it could well translate the calorimetric and spectroscopic phenomena into the underlying physical knowledge. Interactions between THP and phospholipids can play a critical role in the liposomal drug delivery system, especially in the safety mechanism elucidation and rational formulation design.