Objective To study the condition and method of hydrodynamics-based transgene(HDT) in rat fatty liver. Methods Inject different dosages and concentrations of green fluorescent protein plasmid pEGFP-C1 at different speeds, then collect 4 rats’ liver leaves at different time points after injection and prepare their frozen section, finally observe and quantify the GFP expression with fluo rescence microscope at 488 nm excitation wavelength. Results Plasmid pEGFP-C1 concentration 33mg/L, injection speed 2ml/s, injection volume 8.5%of rat body weight, injected plasmid. After 6 hours of injection, GFP-positive cells rate of pedicel leaf is about 18%, left leaf about 14%, middle leaf about 12.5%, right leaf about 10% and tail leaf about 8%. GFP begin to gradually reduce since 24 hours, until 72 hours almost no GFP-positive cells were checked in all liver leaves. Conclusion Hydrodynamics-based transgene can be applied to rat fatty liver, the appropriate conditions of this method are 33mg/L plasmid concentration, 8.5% rat avoirdupois, 2ml/s injection speed, and the suitable time to observe the proportion of GFP-positive cells is 6-24 hours after gene injection.