Objective To study the conditions and methods of hydrodynamicsbased transgene into rat regenerating liver EM>in vivo/EM>. Methods The solution with concentration 30mg/L genecontaining plasmid was injected into rat tail veins at a speed of 2ml/s, then partial hepatectomy (PH) was performed at different times before/after injection, finally the rat (g) and regenerating liver (g) were weighed, and the liver coefficient (LSUP>c/SUP>) was calculated. Out of 15 groups which are LSUP>c/SUP>±LSUP>c/SUP>*0%, *5%, *10%, *15%, *20%, *25%, *30%, *35%, the most suitable group was chosen as correction coefficient to calculate the most appropriate volume of plasmid solution which was injected into the regenerating liver at different recovery times, and at the same time, right lobe of liver was gathered to make frozen section, then observe and quantify the positive green fluorescent protein (GFP) rate at 488 nm excitation wavelength. Results Injection of either physiological saline or empty plasmid has no significant difference compared with control (only PH performance). The appropriate time of hydrodynamicsbased transgene is more than 12 hours before PH or anytime after PH. The solution volume of hydrodynamicsbased transgene into liver regenerating rat after PH is rat weight (g) ×9%×1/3×corresponding correction coefficient (Trc). Both vector and target gene have effect on the time and abundance of