Abstract: A novel chitosan derivate,urocanic acid-modified chitosan (UAC) was binding plasmid DNA (pDNA) to prepare nano-complexes.The ability to form nano-complexes was evaluated by gel retardation assay；the factors (including pH value,osmotic pressure,nuclease and heparin) on the stability of the nano-complexes was assessed；finally,the particle size,Zeta potential and the morphology of preferred nano-complexes were characterized.The results showed that UAC of high substitution value (50%) can form nano-complexes with pDNA completely when N/P≥3,and the stability of the nano-complexes against alkaline environment,high osmotic pressure,DNase I and heparin was better at higher N/P；UAC of low chitosan molecular weight (20 kD) had higher protection for pDNA from DNase I,and UAC/pDNA nano-complexes were easily disaggregated by heparin.The nano-complexes at N/P 30 were approximatively spherical in shape,the particle size and Zeta potential were 125.2 nm and +37.9 mV,respectively.Therefore,the nano-complexes prepared with UAC of low chitosan molecular weight and high substitution value at high N/P could be suitable for cell transfection,and might be a novel potential gene-loaded nano-complex.