Objective To study the condition and method of hydrodynamics-based transgene when applied to gene transfection in rat liver. Methods Inject different dosages and concentrations of green fluorescent protein (GFP) plasmid (pEGFP-C1) at different speeds, then collect 4 rats’ liver leaves at different time points after injection for frozen section, and to observe and quantify the GFP expression with a fluorescence microscope at 488 nm excitation wavelength. Results With one-off injection(the optimal conditions), plasmid concentration is 30mg/L, injection speed is 2ml/s, injection volume is 9％ of rat body weight. At 6 hours after injection, GFP-positive cells take on the highest proportion of above 20％; GFP begin to gradually reduce since 24 hours, until 72 hours almost no GFP-positive cells are seen in any liver leaf. Briefly(under the above optimal conditions), GFP expression in each liver leaf is described as follows: about 30％ for pedicel leaf, about 20％ for all of left, middle and right leaves,and about 10％for tail leaf.Conclusion Conclusion Hydrodynamics-based gene delivery procedure can be well applied to transgene in the rat liver, with the appropriate conditions of this method being 30mg/L plasmid concentration, 9％rat avoirdupois, 2ml/s injection speed. The most suita