Potential application of CNT in medical science is the essence of this research. Interaction of CNT and Li doped CNT with Aspirin as a drug was studied in gas phase and in aqueous solution. Aspirin anion and neutral Aspirin were considered in physiological media. Each species was first modeled by quantum mechanical calculations, and then their properties in aqueous solution were studied by applying Monte Carlo simulations. The results of density functional calculations in gas phase show that only Li doped CNT can interact with Aspirin. Computation of solvation free energies in water showed that solubility of the complexes of Aspirin species with Li doped CNT was larger than CNT. Enhancement of the solubility of CNT improves the medicinal applications of these materials. Calculation of complexation free energies indicated that only Li doped CNT produce the stable complex in aqueous solution. So CNTLi can be appropriate system as a possible effective drug transporter for Aspirin delivery.