Abstract: To prepare doxorubicin-loaded N-octyl-N′-succinyl chitosan polymeric micelle (DOX-OSC) and study the biodistribution of DOX-OSC in mice, DOX-OSC was prepared by dialysis method. By using doxorubicin injection (DOX-INJ) as control, DOX-OSC and DOX-INJ were administered to mice through caudal vein at a dose of 5 mg·kg^-1 body weight. The RP-HPLC method was established to determine the DOX levels in the plasma and other tissues of mice. The tissues distribution and targeting efficiency were evaluated by pharmacokinetic parameters (AUC, MRT) and targeting parameters (R_e, C_e and T_e). The drug loading and entrapment efficiency of DOX-OSC were (35.8±0.4)% and (75.3±1.1)%, respectively. The diameter and zeta potential of DOX-OSC were (174±12) nm and (-37.1±3.0) mV, respectively. The transmission electron microscope result showed DOX-OSC with spherical shape. The biodistribution results showed that the concentration of DOX of both DOX-OSC and DOX-INJ decreased rapidly in blood after iv administration. While free DOX levels in blood at 12-96 h were not detectable for DOX-INJ, in contrast, DOX level in blood at 96 h was still found for DOX-OSC. In contrast to DOX-INJ group, DOX-OSC showed a higher targeting efficiency in the liver and spleen. The AUCs of DOX in the liver and spleen were 20.0 and 47.4 times and the MRT were 11.2 and 37.2 times, respectively. And the levels of DOX-OSC in the heart and kidney tissues were significantly reduced. And the drug distribution of DOX-OSC in the heart and kidney tissues were 17.0% and 11.4%, respectively. Hence, DOX-OSC shows an excellent drug loading capabilities and a higher targeting efficiency in the liver and spleen. That the levels of DOX-OSC in the heart and kidney tissues are significantly reduced, might improve the treatment efficacy of DOX and decrease the side effects.