Objective: To prepare fluorescent nano gene vectors for traceable gene delivery and evaluate the biocompatibility of the nanoparticles. Methods: The fluorescent nanopaticles were constructed by quantum dots (Qdots) encapsulated by chitosan, then characterized by transmission electron microscopy (TEM), fluorospectrophotometer, zeta potential and Fourier transform infrared spectrometry (FTIR). The imaging of tumor-injected xenograft nude mouse was taken to evaluate the in vivo fluorescent signal of CS-Qdots nanoparticles. Gel retardation assays were used to test the DNA binding affinity of CS-Qdots. The expression of green fluorescent protein (GFP) gene delivered in cells by CS-Qdots was observed by confocal laser microscope. The biocompatibility of CS-Qdots was evaluated by cells relative grow rate (RGR) of MTT test, hemolysis rate and acute toxicity tests in mice. Results: The mean particle size of the CS-Qdots nanoparticles was 20-30 nm in the TEM image and the surface charge of them was （28.02 ± 1.15） mV. The characteristic peaks of chitosan were observed on the CS-Qdots FTIR spectra. The light emission peak of CS-Qdots was at 630 nm. Complete retardation was observed for particle-DNA weight ratios over 10∶1, for which the DNA was well packed in the gene-CS-Qdots complexes with a positive surface charge. High level expression of GFP genes delivered into HepG2 cells by CS-Qdots was detected by a confocal laser microscopy. The strong fluorescence signal of CS-Qdots in vivo was observed in xenograft nude mouse imaging. The MTT results indicated that RGRs of cells co-incubated with CS-Qdots at concentrations of 50, 100, 200 and 400 μg/mL were 1.000, 1.000, 0.917, and 0.875, respectively. The RGRs of cells co-incubated with Qdots at the corresponding concentrations were 1.000, 0.850, 0.621 and 0.326. The hemolysis rates of Qdots over the concentration of 100 μg/mL were all above 5%. Oppositely, the hemolysis rates of CS-Qdots were all below 5% at all the concentrations tested. The results of acute toxicity tests in mice at 72 h post injection indicated that compared to the saline-controlled mice, no symptoms of main organ lesions were observed, no abnormality was seen in the blood cells test, and the functions of liver and kidney were normal in the mice. Conclusion: The CS-Qdots fluorescent nanoparticles with high biocompatibility were constructed successfully, which delivered genes into cells efficiently. The nano gene vectors could be traced by fluorescent imaging in vivo and in vitro.