Abstract: The aims of this research were to constitute and evaluate one targeting anticancer co-delivery system for both micro-molecularchemotherapeutic drugs(docetaxel, DTX)and small interfering RNA(siRNA)expressed by COX-2. The nanoparticles composed of poly(D, L-lactide-co-glycolide)(PLGA)bearing disulfide-linkaged reducible polyethyleneimine(PEIss)covered by hyaluronic acid(HA). Meanwhile, HA-PEI-PLGA nanoparticles were prepared as control. Firstly, the solvent evaporation was used to the particles which exhibited a core-shell structure with a uniform size of 150-200 nm. The cumulative drug release in two kinds of PBS media(pH 7. 4 and pH 5. 0)during 72 hours indicated that DTX-loaded nanoparticles had sustained-release effect within 24 hours. The cumulative release of DTX of HRPSP NPs in PBS pH 5. 0 was 10%-25% more than that in PBS pH 7. 4, which demonstrated that favored release of DTX from nanoparticles could be achieved in acidic tumor microenvironment. Then, the highest transfection efficiency was observed after 14-16 h incubation at N/P ratio of 40/1. Following the saturation of CD44 receptor, the mean fluorescence intensity of HRPSP NPs from the cells decreased drastically in the case of saturation with free HA before. However, there existed no significance in the fluorescence of RPSP NPs between the cells with and without saturation with free HA, which indicated the nanoparticles′ targeting potential toward tumor cells. In the Western blot, the relative silencing efficiency of Bcl-2, bax, capase-3 and COX-2 mRNAprotein was calculated. In comparison to the control group, the silence efficiencies of bax and capase-3 were both significantly increased while that of Bcl-2 was evidently reduced, particularly in siCOX-2/HRPSP NPs group(P< 0. 01). The similar results were obtained in the silence efficiency of COX-2 protein in which the COX-2 quantity on mRNA and protein decreased. The results suggest that the nanoparticles could achieve the synergistic effect on the combinatorial delivery of siRNA and lipophilic anti-tumor drugs.